random Bytes

github_api gem with Rails 4: How to import github user information to your Rails Application

2013-08-28T21:51:00.001-07:00

This time i am back with one more API feature to the list , that we can incorporate with the existing Rails 4 Application. github api gem is the Ruby wrapper for the GitHub REST API v3.It supports almost all the API methods provided by Github.

Refs
https://github.com/peter-murach/github
https://github.com/rest-client/rest-client

Gemfile

Add gem 'github-api' & gem 'rest-client' to your Gemfile. 'rest-client' gem is a simple HTTP and REST client for Ruby. It will help you to get the response data from github after attaching the access token.

Github Controller

As you all know the basic API authentication and after that returning the user back to the callback method, here also there no much changes in the basic functions .First it will authenticate the user to the github app , after that it will redirect the user back to the callback method that we have specified in the redirect url with an authorization code as params , by using the authorization code returned from the github , we will be able to generate a github client object and we can call the get_token method by passing the authorization code as an argument . It will return the Access token to you . by using the access token you can easily call the Git API link by attaching the access token. It will give you the whole user Repository list as JSON.

Route File

View file

Linkedin Gem with Rails 4 : How to Import Linkedin user information to your Rails Application

2013-08-28T04:58:00.000-07:00

All your Linkedin Information's are now just a mouse click away. by using linkedin gem with Rails we can easily import all your linkedin information's like your skills , contact details , experience details, education details , project details , connection details etc. Now almost all popular websites mainly working in the Professional Networking platform are providing this feature , http://careers.stackoverflow.com/ is my favorite among them , which does the job very brilliant.

Refs

  https://github.com/pengwynn/linkedin
  http://developer.linkedin.com/documents/profile-fields
  https://gist.github.com/sreeharikmarar/6364970

Gemfile

  gem 'linkedin', '0.4.2', :git => "git://github.com/pengwynn/linkedin.git"

Linkedin Controller

As you all know the basic authentication and the Callback methods , here also first it will authenticate the user with the linkedin app . You can specify the user access information here in the Linkedin Configuration .What all user fields that your application want to get access. After Authenticating the user it will redirect the user back to the callback method with oauth_verifier as parmas. you will be able to create Access token and access token secret by using the linkedin client object that we have created using the response parameter.

Once the linkedin Client object creation is done , you will be able to access all the user information's like contact details , skills , education details , experience details etc , All the profile field information's are available at http://developer.linkedin.com/documents/profile-fields

LinkedIn is very particular about access to profile fields and you cannot combine multiple fields which requires 2 different type of access. so when you try to get just position details by c.profile(:fields => %w(positions)) it assumes the access of type 'r_basicprofile' whereas educations field require access of type 'r_fullprofile'.so try 2 seperate API calls to retrieve both fields.

"first_name","last_name","headline","positions" available for 'r_basicprofile' member permission,so they can be combined together. but "educations", "three_current_positions", "three_past_positions" , "certifications" etc are available in 'r_fullprofile' . So you have to separate the API calls with respect to the requirements.

Route File

View File

Integrate Dropbox with your Rails App by using Dropbox API gem with Paperclip

2013-07-19T21:18:00.000-07:00

We are going to steal all the Dropbox documents by using Dropbox API with the help of Paperclip. Hey got scared !! .. Oh pls .. just kidding. But seriously ,We can do that with the help of dropbox-api gem & paperclip .

Step 1

Create an App in Dropbox Developer to get the key-Secret pair. You have to set the permission type to "Full Dropbox" mode to get the full Read/Write Access to any file inside the user's Dropbox.

Step 2

Setup your Rails App , include these 2 gems in your Gemfile.
gem 'dropbox-api'
gem "paperclip"

Step 3

Create a file in your config/initializers directory and name it dropbox.rb and put the following line of code inside.

Dropbox::API::Config.app_key    = 'APP KEY'
Dropbox::API::Config.app_secret = 'SECRET KEY'
Dropbox::API::Config.mode       = "dropbox"

Step 4

we have to create Paperclip model for downloading the Files from Dropbox and create the same in your app in Rails way.

class DropboxFiles < ActiveRecord::Base

   attr_accessible :url , :created_at ,:updated_at, :document

   has_attached_file :document ,

    :url => "/system/:class/:attachment/:id/:style/:basename.:extension",
    :path => "#{Rails.root}/public/system/:class/:attachment/:id/:style/:basename.:extension",
    :storage => ((Rails.env.production? || Rails.env.staging?) ? :s3 : :filesystem)

end

Step 5

Controller and Callback Actions for authenticating the user first to Dropbox and redirecting the user back to the callback action to perform the Downloading Activities.

routes.rb

match '/dropbox/authorize'   => 'dropbox#authorize' , :method => :get , :as => :dropbox_auth
match '/dropbox/callback' => 'dropbox#callback' , :method => :get , :as =>  :dropbox_callback

dropbox_controller.rb

I will brief you the functions written inside Dropbox controller.

authorize Action will authorize the user with App and will redirect the user back to the Callback action. Callback Action will give you the secret token pair as a response . We can create a Dropbox client object with access token & secret token pair .

Now we are ready to download the entire documents ( One after another ) belongs to that particular user.

We will list all the documents and will iterate inside a loop . this time we will check whether the document is a File or a Directory . it will call the function recursively until it reaches a File object .

If it is a File object then will call download_and_create(obj) function and will pass the same File obj as an argument. Inside download_and_create(obj) function we will again call one more function named download_file_from_url and will pass the same argument .The File object that we passed as an argument has one instance method named "redirect_url" , we can get the full Dropbox path of that particular document by calling "redirect_url.url" method.

download_file_from_url action will download the file first to Server and will return the absolute path of the downloaded file. So now the File is there in our Rails App. we can create a Paperclip file Object by using DropboxFiles model , DropboxFiles.create(:document => dp_file). here we are passing the absolute file path as an argument.It will create same File in Our Rails application. Don't forget to remove the file from your Rails root path after creating the Paperclip Object.

So that's it , hope you guys will try this . There are lot of options that we can try out with Dropbox-api gem. I have not optimized the code , hope you guys will do it for me. so have fun coding ...

Linkedin Gem for Rails : How to share dynamic contents to Linkedin from your Rails Application

2013-05-08T03:13:00.000-07:00

After Facebook & Twitter share ,its time for Linkedin. I would suggest you to refer my 2 prev posts before going through this article.

Include "linkedin" gem in your Gemfile and bundle .

gem 'linkedin'

Route file:

 match '/linkedin_share/auth'   => 'linkedin_share#auth' , :method => :get , :as => :linkedin_auth

 match '/linkedin_share/callback' => 'linkedin_share#callback' , :method => :get , :as =>  :linkedin_callback

LinkedinShare Controller & Actions :

class LinkedinShareController < ApplicationController

  def init_client
    
    key = "APP KEY"
    secret = "SECRET KEY"

    linkedin_configuration = { :site => 'https://api.linkedin.com',
        :authorize_path => '/uas/oauth/authenticate',
        :request_token_path =>'/uas/oauth/requestToken?scope=rw_nus',
        :access_token_path => '/uas/oauth/accessToken' }

    @linkedin_client = LinkedIn::Client.new(key, secret,linkedin_configuration )
  end

  def auth
    init_client
  
    cookies["title"] = { :value => "#{params[:title]}", :expires => 1.minute.from_now }
    cookies["url"] = { :value => "#{params[:url]}", :expires => 1.minute.from_now }
  
    request_token = @linkedin_client.request_token(:oauth_callback => "http://#  {request.host_with_port}/linkedin_share/callback")
    session[:rtoken] = request_token.token
    session[:rsecret] = request_token.secret
  
    redirect_to @linkedin_client.request_token.authorize_url
  end

  def callback
    init_client
  
    if session[:atoken].nil?
      pin = params[:oauth_verifier]
      atoken, asecret =  @linkedin_client.authorize_from_request(session[:rtoken], session[:rsecret], pin)
      session[:atoken] = atoken
      session[:asecret] = asecret
    else
      @linkedin_client.authorize_from_access(session[:atoken], session[:asecret])
    end

    c = @linkedin_client
    
    title = "#{cookies["title"]}"
    url = "#{cookies["url"]}"

    c.add_share({
        :comment => title,
        :content => {
          :title => title,
          :submitted_url => url,
          :submitted_image_url => "IMAGE PATH",
          :description => 'YOUR DESCRIPTION'
        }
      })

    redirect_to root_path
  end
end

Twitter gem for Rails : How to share dynamic contents to Twitter from your Rails Application

2013-05-08T02:46:00.000-07:00

Before going through this post . I would suggest you to go through my previous FB share post. You will get to know the basic functionality & working from the prev post .After that please go through Twitter gem description.

I hope you have gone through the prev post and you have got some idea about it.

Now we will start with Twitter share implementation.You have to include "twitter" & "oauth" gems into your Gemfile.

gem 'twitter'

gem 'oauth'

Compared to FB share , here we need to include "Oauth" gem for authenticating the user to twitter and redirect the user back to your applications Callback action.After getting the Oauth Secret Key i.e returning from Twitter you can configure the Twitter gem settings and you can post to twitter from your Rails app.
Route :

  match "/twitter_share/auth" => "twitter_share#auth"  , :method => :get , :as => :twitter_auth

  match "/twitter_share/callback" => "twitter_share#callback"  , :method => :post , :as => :twitter_callback

Twitter Share Controller & Actions :

 def auth

    cookies["title"] = { :value => "#{params[:title]}", :expires => 1.minute.from_now }

    cookies["url"] = { :value => "#{params[:url]}", :expires => 1.minute.from_now }

 
    consumer_key = "APP ID"

    consumer_secret = "SECRET KEY"

    oauth_consumer = OAuth::Consumer.new(consumer_key, consumer_secret,

      :site => 'http://api.twitter.com',

      :request_endpoint => 'http://api.twitter.com',

      :sign_in => true)

    request_token = oauth_consumer.get_request_token(:oauth_callback => "http://#{request.host_with_port}/twitter_share/callback")


    session[:request_token] = request_token.token

    session[:request_token_secret] = request_token.secret

    redirect_to request_token.authorize_url

  end

  def callback 

    consumer_key = "APP ID"

    consumer_secret =  "SECRET KEY"

    oauth_consumer = OAuth::Consumer.new(consumer_key, consumer_secret,

      :site => 'http://api.twitter.com',

      :request_endpoint => 'http://api.twitter.com',

      :sign_in => true)

    r_token = session[:request_token]

    r_stoken = session[:request_token_secret]

    atoken = OAuth::RequestToken.new(oauth_consumer,r_token, r_stoken).get_access_token(:oauth_verifier => params[:oauth_verifier])


    Twitter.configure do |conf|

      conf.consumer_key = consumer_key

      conf.consumer_secret = consumer_secret

      conf.oauth_token = atoken.token

      conf.oauth_token_secret = atoken.secret

    end

    Twitter.update("My new post on  #{cookies["title"]}  #{cookies["url"]}")

    redirect_to root_path

  end

Fb Graph Gem for Rails : How to Post dynamic contents to Facebook Wall from your Rails Application

2013-05-07T06:11:00.005-07:00

This post will introduce the usage of fb_graph Gem with your existing Rails Application.fb_graph has already done a lot for you guys to exploit the FB API features with your Rails Application , you can have an eye on this fb_graph Gem before going through this post.

Suppose you have a blogger kind of application, and when you compose a new post , you would like to share the same in your Facebook wall, and also would like to give the same option for all the users ,those who liked your post and would like to share the same in their Facebook Wall.

I think now almost all the websites are using this feature to increase their user traffic , to popularize their sites, Since Facebook turned out to be a great option for advertising and marketing your site content.

One day i also felt the same and after one complete days of effort ..... i was successful. I thought i should share the same for you guys to reduce your one days effort ( or may be less ) for implementing this FB share option.

I hope i am not boring you , anyway stop to all kind of rubbish introduction and lets start coding ..

As usual first of all add fb_graph Gem to your Gemfile

gem 'fb_graph'

After that we have to create 2 actions for authenticating the User to Facebook and After authenticating the user we need a Callback action and this will share the Contents to that particular Users Facebook Wall.

Here we start from the Route file , mention your roots and controller actions here.

route file

 match "/fb_share/auth" => "fb_share#auth"  , :method => :get , :as => :fb_auth

 match "/fb_share/callback" => "fb_share#callback"  , :method => :get , :as => :fb_callback

Before get in to the serious part , i would like to tell you more about How i implemented this or what was my requirement.

Like i said before , suppose we have a blogger application , we are going to display the FB share button just below each post.

Requirements

When user clicks on the share button, it should redirect the user to Facebook login, and after allowing the permission to post , The content should post on the Users FB Wall.
Contents should be,

Title of my Blogpost.
Title should be a link to my Blog Posts detail page.
Small Descrition.
Thumbnail Image (If you want ).

Steps

When User clicks on share button, We should call an action and here that probably be an Auth Action.
But after authorizing the user , Facebook will redirect the user back to our Applications Callback action . So at that time , from where will we able to get the Contents like (Title , Description , URL, Image path) ?
For that reason , i just implemented a cookie for storing all these information .
When User Clicks on share button , We will pass all these information to Auth action.We Will Assign all these details to Each cookie.
After Authenticating the User with (Key , Secret) pair, Facebook will redirect the user back to the Callback Action with Authorization code.
Then we will call the feed action provided by the FB gem and will assign all these contents like ( Title, Description , image path & URL) from the cookie .
The Rest of the things you dont need to care about . FB Gem will do it for you.

FBShare Controller Actions

class FbShareController < ApplicationController


  def auth

     cookies["title"] = { :value => "#{params[:title]}", :expires => 1.minute.from_now }
     cookies["url"] = { :value => "#{params[:url]}", :expires => 1.minute.from_now }
     cookies["desc"] = { :value => "#{params[:desc]}", :expires => 1.minute.from_now }

   

  @client = client

    redirect_to @client.authorization_uri(
      :scope => [ :offline_access , :publish_stream]
    )

  end


  def callback

    @client = client
    @client.authorization_code = params[:code]

    access_token = @client.access_token! :client_auth_body # => Rack::OAuth2::AccessToken

    me = FbGraph::User.me(access_token)

    title = cookies["title"]
    url = cookies["url"]
    desc  = cookies["desc"]

    me.feed!(

        :message =>  title ,
        :picture => / Your Image path / ,
        :link => url,
        :name => title,
        :description => desc
    )

    redirect_to root_path ( You Application Action path After sharing the content to FB)

  end


  private


  def client

    key = "APP KEY"
    secret = "SECRET KEY"
    fb_auth = FbGraph::Auth.new(key, secret)
    client = fb_auth.client
    client.redirect_uri = "http://#{request.host_with_port}/fb_share/callback"

    client

  end

end

Checkout my Twitter & Linkedin Share posts also ...

Ruby On Rails: Omniauth Devise Authentication using Facebook , Google & Twitter.

2013-01-17T02:32:00.000-08:00

This post is just a simple straightforward description of Omniauth:Overview , intended for the beginners , those who wants to try the OmniAuth for the first time with Facebook , Google & Twitter. This post will cover all the basic information i.e From creating the app in Facebook, Google & Twitter for getting the secret key To connect these Apps to your Rails Application.

Things in common :

add Devise & omniauth gem to your Gemfile.

gem 'omniauth'
gem 'devise'

First of all install Devise into your application.

rails generate devise:install

You have to create user model using devise ,

rails g devise user

and after that we need to add 2 more columns i.e "uid" and 'provider' to our user model.

rails g migration AddColumnsToUsers provider:string uid:string
rake db:migrate

also dont forget to add ":provider" and ":uid" to your attr_accessible also.

We have done with the things that is common in authentication using facebook,Google, Twitter.

We will start with Facebook Authentication first

Facebook Authentication :

add gem 'omniauth-facebook' to your gem file.

First of all you need to create an application in facebook to get the secret key out .

Next, you need to declare the provider in your (config/initializers/devise.rb) and require it

require "omniauth-facebook"
config.omniauth :facebook, "APP_ID", "APP_SECRET"

if you have done with all the above , you need to make your model (e.g. app/models/user.rb) omniauthable:

devise :omniauthable

Better restart your server to recognize the changes you have made in Devise Initializer.

Now Devise will create the following url methods.

user_omniauth_authorize_path(provider)
user_omniauth_callback_path(provide)

use the below line of code in your view file wherever you want to provide the Facebook link to authorize for the users.

<%= link_to "Sign in with Facebook", user_omniauth_authorize_path(:facebook) %>

When the user clicks on the above link, they will redirects to the Facebook login page, after entering their credentials it will again redirect the user back to our applications Callback method . Its time to create Callback method for our application.

To implement the callback method, first of all we need to again return back to our config/routes.rb file and need to tell Devise , in which controller we are going to create that callback action.

devise_for :users, :controllers => { :omniauth_callbacks => "users/omniauth_callbacks" }

Now we we are going to add a new controller file inside our Rails controller directory "app/controllers/users/omniauth_callbacks_controller.rb" and put the following line code in your omniauth_callbacks_controller.rb file.

We will start with Facebook provider first .You have to care about one thing that the action name should be the same as the provider name.

class Users::OmniauthCallbacksController < Devise::OmniauthCallbacksController
  def facebook
    # You need to implement the method below in your model (e.g. app/models/user.rb)
    @user = User.find_for_facebook_oauth(request.env["omniauth.auth"], current_user)

    if @user.persisted?
      sign_in_and_redirect @user, :event => :authentication #this will throw if @user is not activated
      set_flash_message(:notice, :success, :kind => "Facebook") if is_navigational_format?
    else
      session["devise.facebook_data"] = request.env["omniauth.auth"]
      redirect_to new_user_registration_url
    end
  end
end

What is happening inside this callback action ?

When the user enters the credentials in the Facebook sign in form, Facebook actually returns the default information's regarding the particular user , and all that information's retrieved from Facebook by omniauth will be available as a hash at request.env["omniauth.auth"]. try to print this hash for better understanding of what information's are retrieved from Facebook.
Then we are actually calling a method in user model (we are going to add soon ) with request hash as an argument.If the user logs in for the first time "find_for_facebook_oauth()" function will create a new entry in our user model,when the new user user has been saved properly in our database, it return that user and assigns to an instance variable @user.
If the User model returns a valid user , we should sign in and redirect that user to our application , that is why we are passing the :event => :authentication to the sign_in_and_redirect method to force all authentication callbacks to be called.
In case the user is not persisted , we store the omniauth data in the session.Notice we store this data using "devise." as key namespace. This is useful because Devise removes all the data starting with "devise." from the session whenever a user signs in, so we get automatic session clean up. At the end, we redirect the user back to our registration form.
Suppose you doesn't want to provide an external registration event (i.e you want to remove the Registerable module from your app ) . you can comment the Registerable module in the devise User model, it will automatically removes all the links and routes to the registration page. and after that we can redirect to root_path if the user is not persisted.

Now we are going to implement the find_for_facebook_oauth method in our user model (e.g. app/models/user.rb) :

def self.find_for_facebook_oauth(auth, signed_in_resource=nil)
    user = User.where(:provider => auth.provider, :uid => auth.uid).first
    if user
      return user
    else
      registered_user = User.where(:email => auth.info.email).first
      if registered_user
        return registered_user
      else
        user = User.create(name:auth.extra.raw_info.name,
                            provider:auth.provider,
                            uid:auth.uid,
                            email:auth.info.email,
                            password:Devise.friendly_token[0,20]
                          )
      end
      
    end
  end

Here you will find some changes compared to the github omniauth documentation.the reason why i have made these changes , you can get it from this stckoverflow question .

The method above simply tries to find an existing user by using the provider , but if the user is already registered in our application using the same email id but different provider, then we need to restrict the user from creating again the same user entry, otherwise if the user tries to register with the same email account but different provider, Devise will throw error and will restrict the user from signing in to our application. so that is why we are checking again whether the use have already signed in our application using any provider and we have created the user entry in our application. suppose if we finds the registered user , we need to return the registered user, else if the user is not at all registered in our application we are actually creates that user with attributes name, provider, email and with a random password.

So that is all you want , we have completed the Facebook authentication using omniauth.

Google Authentication :

This is just the same as Facebook authentication, first of all you need to register your app in Google to get the API key.

You need to update the redirect uri for the API access, if you are using localhost use the following " http://localhost:3000/users/auth/google_oauth2/callback " like shown in the image.

add 'gem 'omniauth-google-oauth2' ' to your Gemfile. then bundle install

require it in 'config/initializers/devise.rb'

require "omniauth-google-oauth2"
config.omniauth :google_oauth2, "APP_ID", "APP_SECRET", { access_type: "offline", approval_prompt: "" }

Add the following link to your view file where you want to put the google sign in option.

<%= link_to "Sign in with Google", user_omniauth_authorize_path(:google_oauth2) %>

When the user clicks on the above link, they will redirects to the Google login page, after entering their credentials it will again redirect the user back to our applications Callback method.

Inside "omniauth_callback_controller" add the following function "google_oauth2"

class Users::OmniauthCallbacksController < Devise::OmniauthCallbacksController
  def google_oauth2
    
    @user = User.find_for_google_oauth2(request.env["omniauth.auth"], current_user)

    if @user.persisted?
      flash[:notice] = I18n.t "devise.omniauth_callbacks.success", :kind => "Google"
      sign_in_and_redirect @user, :event => :authentication
    else
      session["devise.google_data"] = request.env["omniauth.auth"]
      redirect_to new_user_registration_url
    end
  end
end

Inside the user model. "app/models/user.rb"

def self.find_for_google_oauth2(access_token, signed_in_resource=nil)
    data = access_token.info
    user = User.where(:provider => access_token.provider, :uid => access_token.uid ).first
    if user
      return user
    else
      registered_user = User.where(:email => access_token.info.email).first
      if registered_user
        return registered_user
      else
        user = User.create(name: data["name"],
          provider:access_token.provider,
          email: data["email"],
          uid: access_token.uid ,
          password: Devise.friendly_token[0,20]
        )
      end
   end
end

Google Authentication is now ready to use.

Twitter Authentication :

Important thing in Twitter authentication is Twitter will not provide you email address for any reason , so for the authentications like we did in Facebook and Google, we cant identify a user by using an email whether the user is already registered (i.e have already created in our application) or not.

What i did here is , i have created a fake email by appending the provider id with the domain string "twitter.com" like "2312234@twitter.com".this will be a unique entry.but this also will not solve our problem, because ones the user have registered in our application for the first time the twitter account , we cant get the email that is for sure , but we are creating one with provider id and domain that is also fine. but we cant identify the user whether he is already registered or not when he/she tries to login for the second time by using Facebook or Google provider.

If you are fine with it you can go forward, i know this is not a good solution. but here we cant leave the column email as blank, we have to enter something in email column when creating a user.

So first of all creates your twitter application here for getting the API key. put the website field as the following "http://127.0.0.1:3000/" if your are using localhost and callback URL also as following "http://127.0.0.1:3000/auth/twitter/callback".

Add the gem gem 'omniauth-twitter' to your Gemfile. and bundle install.

Require it in "config/initializers/devise.rb"

require 'omniauth-twitter'
config.omniauth :twitter ,"APP_ID", "APP_SECRET"

Add the following link to your view file for twitter sign in option.

<%= link_to "Sign in with Twitter", user_omniauth_authorize_path(:twitter) %>

When the user clicks on the above link, they will redirects to the Twitter login page, after entering their credentials it will again redirect the user back to our applications Callback method.

Inside "omniauth_callback_controller" create a function named "twitter" like following,

class Users::OmniauthCallbacksController < Devise::OmniauthCallbacksController
  def twitter
    auth = env["omniauth.auth"]
    #Rails.logger.info("auth is **************** #{auth.to_yaml}")
    @user = User.find_for_twitter_oauth(request.env["omniauth.auth"],current_user)
    if @user.persisted?
      flash[:notice] = I18n.t "devise.omniauth_callbacks.success"
      sign_in_and_redirect @user, :event => :authentication
    else
      session["devise.twitter_uid"] = request.env["omniauth.auth"]
      redirect_to new_user_registration_url
    end
  end
end

inside your "User" model, add the following method.

  def self.find_for_twitter_oauth(auth, signed_in_resource=nil)

    user = User.where(:provider => auth.provider, :uid => auth.uid).first
    if user
      return user
    else
      registered_user = User.where(:email => auth.uid + "@twitter.com").first
      if registered_user
        return registered_user
      else
        user = User.create(name:auth.info.name,
          provider:auth.provider,
          uid:auth.uid,
          email:auth.uid+"@twitter.com",
          password:Devise.friendly_token[0,20]
        )
      end
    end
  end

That is all you need about Facebook,Google & Twitter authentication! , try it yourself , have fun coding.

Operator Overloading in Ruby

2012-12-09T23:54:00.002-08:00

I expect many of you know that Ruby permits Operator overloading .Many of Ruby's operators are implemented as methods, you can define or redefine how these methods or operators should work in your own classes , here i am trying to mention some fun facts that we can do with ruby.

I expect all of you should be knowing this , may be better than me as well . But this is a just a simple but strait forward example for the beginners like me, those who wanted to experiment more on Ruby.

Creating a class called ClassA

class ClassA
  attr_accessor :value
  def initialize(value)
    @value = value
     puts "Object of ClassA with value #{@value} has been created"
  end
 end

and Instantiating one obj of ClassA,

a=ClassA.new(10)
Object of ClassA with value 10 has been created

What if ruby permits a behavior like you can add objects of 2 different classes , then you are receiving the output without creating any scene , it will be fun right.

Creating another class called ClassB,

class ClassB
  attr_accessor :value
  def initialize(value)
    @value = value
     puts "Object of ClassB with value #{@value} has been created"
  end
 end

and instantiating the ClassB obj like,

b=ClassB.new(20)
Object of ClassB with value 20 has been created

Now we are overloading the behavior of '+' operator by defining a function like ,

class ClassA
  attr_accessor :value
  def initialize(value)
    @value = value
     puts "Object of ClassA with value #{@value} has been created"
  end
  def +(obj)
    return ClassA.new(self.value + obj.value)
  end
 end

class ClassB
  attr_accessor :value
  def initialize(value)
    @value = value
     puts "Object of ClassB with value #{@value} has been created"
  end
  def +(obj)
    return ClassB.new(self.value + obj.value)
  end
 end

What will happen if we are performing an addition using these 2 objects a & b,

c = a + b

the fun begins here,

try to print c.value you will get the value 30,

How this magic happens ,

Operators are just methods in Ruby , all the arithmetic operators are behaves like methods and we are passing values as arguments , like in the above example a + b , we are calling the method called '+' and passing b as an argument . This is same with all the arithmetic operators.

If you have created 3rd class also like ClassC, and have created obj c = ClassC.new(30)
You will get the results while trying all the possible way like,

a+b+c
a+(b+c)
(a+b)+c

Ruby on Rails : How to include a page specific JavaScript file in Rails 3.1?

2012-03-24T01:10:00.004-07:00

Rails 3.1 application has a new effective way to include a JavaScript file for a particular page without compromising the loading time by using Asset pipeline.

You all know that in previous versions of Rails, all assets were located in subdirectories of public such as images,javascripts and stylesheets. With the asset pipeline, the preferred location for these assets is now the app/assets directory.Assets can still be placed in the public hierarchy. Any assets under public will be served as static files by the application or web server.

In production, Rails precompiles these files to public/assets by default. The precompiled copies are then served as static assets by the web server. The files in app/assets are never served directly in production.

If you want to add a JavaScript file for a particular page in your Rails 3.1 application,just follow the steps below ,its working fine for me.

Mention the JavaScript file name that you want to access from a particular page in Config -> environments -> production.rb like shown below.

Demo::Application.configure do

       .
       .
   config.assets.precompile += %w( application.css application.js flexpaper.js data_table.js public.js jquery.Jcrop.js jquery.Jcrop.min.js google_org_chart_query_wrapper.js jquery.jstree.js)
       .
       .   
end

Mention the JavaScript file name that you want to include in a particular view page by using the JavaScript include tag like.

<%= javascript_include_tag "jquery.jstree" %>

After that you need to precompile the assets.You all know that Rails comes bundled with a rake task to compile the asset manifests and other files in the pipeline to the disk.Compiled assets are written to the location specified in config.assets.prefix. By default, this is the public/assets directory.

The rake task is:

bundle exec rake assets:precompile

Ruby on Rails :Cropping images in runtime using Jcrop & ImageMagick

2012-01-23T23:38:00.001-08:00

In the previous post i have mentioned about integrating the Jcrop functionality with ImageMagick to hide the selected coordinates of the image using a specific color.But here i am describing on the core feature of Jcrop i.e cropping the image in runtime with the selected coordinates.Here also , we are using ImageMagick in server side to accomplish the whole process.

You all know that Jcrop is a powerful image cropping engine for jQuery. It’s been designed so developers can easily integrate an advanced image cropping functionality directly into any web-based application without sacrificing their time ,flexibility and performance.

ImageMagick is a software suite to create, edit, compose, or convert bitmap images. It can read and write images in a variety of fomats (over 100) like DPX, EXR, GIF, JPEG, JPEG-2000, PDF, PhotoCD, PNG, Postscript, SVG, and TIFF. We can use ImageMagick to resize, flip, mirror, rotate, distort, shear and transform images, adjust image colors, apply various special effects, or draw text, lines, polygons, ellipses and Bézier curves. ImageMagick have a power full command line tool known as “Convert”. Convert has around 265 options for manipulating images .

So now we are going to integrate this two with Rails ,i wont go in depth of how to create the whole process.

In summery :

User choose an image and uploads to a server using paperclip.
Wep app shows the images to user and allows him/her to select the desired piece of selection of the image to hide using Jcrop.
Using an Ajax post request ,we are sending the parameters (X-cord,Y-cord,Height,Width) to the sever which responsible to crop the portion of the image.
The appropriate action in the controller will accept the parameters,and then crop the parameters by using a piece of Image-magic code.

Jcrop Action :

In the client side ,where we are showing the uploaded image to the user.Here we have to add the Jcrop functionality to select the coordinates of the selection that the user want to crop .

Here you could see a button for “CROP” . I will brief you the actions behind this button.The CROP button will captures the desired parameters of the selection on the click event ,and then add it to a list called "crop_list".when the user clicks the button the coordinates will push to the crop_list and then sending the coordinates as a parameter by using an AJAX post request to the desired URL which accepting the parameters.

<img src=" // your image source" id="target" />

<form id="coords"
class="coords"
onsubmit="return false;"
action="http://example.com/post.php">
<div>
<input type="hidden" size="4" id="x1" name="x1" />
<input type="hidden" size="4" id="y1" name="y1" />
<input type="hidden" size="4" id="x2" name="x2" />
<input type="hidden" size="4" id="y2" name="y2" />
<input type="hidden" size="4" id="w" name="w" />
<input type="hidden" size="4" id="h" name="h" />

</div>
<button id = "crop" >CROP</button>


</form>
<div style="clear:both;display: block;height: 5px;" ></div>
 <div id="outer">
  <div class="jcExample">
   <div class="article">
    <div id="interface" style="margin: 1em 0;"></div>

  </div>
 </div>
</div>
</div>



</style>

<script type="text/javascript">
jQuery(function($){

$('#target').Jcrop({
onChange: showCoords,
onSelect: showCoords,
onRelease: clearCoords
});

});
function showCoords(c)
{
$('#x1').val(c.x);
$('#y1').val(c.y);
$('#x2').val(c.x2);
$('#y2').val(c.y2);
$('#w').val(c.w);
$('#h').val(c.h);
};

function clearCoords()
{
$('#coords input').val('');
$('#h').css({color:'red'});
window.setTimeout(function(){
$('#h').css({color:'inherit'});
},500);
};

</script>

Now the crop_list contains all the selected coordinates that the user wants to crop ,and then we are sending all these coordinates to a server using Ajax post request with the selected coordinates as parameters .

<script type="text/javascript">

var crop_list=[];
var cord_list=[];

jQuery(document).ready(function(){
  jQuery("#crop").click(function(){

    var X1 = jQuery("#x1").val();
    var Y1 = jQuery("#y1").val();
    var X2 = jQuery("#x2").val();
    var Y2 = jQuery("#y2").val();
    var W = jQuery("#w").val();
    var H = jQuery("#h").val();

    cord_list= [W,H,X1,Y1];

    crop_list.push(cord_list);

 
    var val = crop_list;
    jQuery.ajax({
      type: "POST",
      url: "/image/crop",
      data: {"cordinates": val},
      complete: function () {
      window.location.reload(true);
      }});
   }):
});

</script>

ImageMagick Action :

Now we comes to the server side.I have created an action called "crop" in my rails application's controller.Here the "crop" action will accept the parameters, and then the magic comes with that snippet of ImageMagic as shown below.

def crop
    cordinates = params["cordinates"]
    image_path = "# specify your image path "
    coordinates.each do |item|
       coordinate = item[1]
       cord = coordinate[0].to_s + 'x' + coordinate[1].to_s + '+' + coordinate[2].to_s + '+' +        coordinate[3].to_s

       system "convert #{img_path} -crop #{cord} #{img_path}"
    end
end.

The main keyword that you have to notice in the above snippet is "crop".The "cord" variable is nothing but the coordinates that we are sending via an ajax post request to the server.The coordinates are nothing but "Height","Width","X-cord","Y-cord".Here we are accepting that coordinates using params key word and assigning it to a variable .Then we have to specify the image_path of the desired image that you wants to crop."crop" keyword will do the cropping function by an amount that we are specified.

Here we are iterating the loop and executing the command number of times equal to the number of selection."System" is the command in ruby to execute shell commands from the script.After executing the above script we will get the modified picture and then as a response we can send it to a client.But here in the Ajax post request i just coded the command to reload the whole page again as response to affect the changes in the client side.Now the client will see the new image with the applied changes.

I have hosted this application in Heroku. Check out the below link,

http://cropimage.herokuapp.com/

Ruby on Rails : Image hiding using Jcrop & ImageMagick

2012-01-12T19:49:00.001-08:00

So now we are going to integrate this two with Rails ,i wont go in depth of how to create the whole process.

In summery :

User choose an image and uploads to a server using paperclip.
Wep app shows the images to user and allows him/her to select the desired piece of selection of the image to hide using Jcrop.
Using an Ajax post request ,we are sending the parameters (X-cord,Y-cord,Height,Width) to the sever which responsible to hide the portion of the image.
The appropriate action in the controller will accept the parameters,and then hide the parameters by using a piece of Image-magic code.

Jcrop Action :

In the client side ,where we are showing the uploaded image to the user.Here we have to add the Jcrop functionality to select the coordinates of the selection that the user want to hide .

Here you could see 2 buttons for “ADD” & “SAVE”. I will brief you the actions behind this buttons.Here we are providing a functionality to user that ,he/she can select multiple selections using Jcrop and then we add it to a list called “cord_list”.Here each time user have to click the add button to store the each selection into a “cord_list”, and after that we are pushing the each selction list into another list called “adj_list”.Now it will act like a list of list.

<img src=" // your image source" id="target" />

<form id="coords"
class="coords"
onsubmit="return false;"
action="http://example.com/post.php">
<div>
<input type="hidden" size="4" id="x1" name="x1" />
<input type="hidden" size="4" id="y1" name="y1" />
<input type="hidden" size="4" id="x2" name="x2" />
<input type="hidden" size="4" id="y2" name="y2" />
<input type="hidden" size="4" id="w" name="w" />
<input type="hidden" size="4" id="h" name="h" />

</div>
<button id = "add" >ADD</button>
<button id ="save" >SAVE</button>%>

</form>
<div style="clear:both;display: block;height: 5px;" ></div>
 <div id="outer">
  <div class="jcExample">
   <div class="article">
    <div id="interface" style="margin: 1em 0;"></div>

  </div>
 </div>
</div>
</div>



</style>

<script type="text/javascript">
jQuery(function($){

$('#target').Jcrop({
onChange: showCoords,
onSelect: showCoords,
onRelease: clearCoords
});

});
function showCoords(c)
{
$('#x1').val(c.x);
$('#y1').val(c.y);
$('#x2').val(c.x2);
$('#y2').val(c.y2);
$('#w').val(c.w);
$('#h').val(c.h);
};

function clearCoords()
{
$('#coords input').val('');
$('#h').css({color:'red'});
window.setTimeout(function(){
$('#h').css({color:'inherit'});
},500);
};

</script>

Now the adj_list contains all the selection coordinates that the user wants to hide ,and then we are sending all these coordinates to a server using Ajax post request with the selected coordinates as parameters .

<script type="text/javascript">

var adj_list=[];
var cord_list=[];

jQuery(document).ready(function(){
  jQuery("#add").click(function(){

    var X1 = jQuery("#x1").val();
    var Y1 = jQuery("#y1").val();
    var X2 = jQuery("#x2").val();
    var Y2 = jQuery("#y2").val();
    var W = jQuery("#w").val();
    var H = jQuery("#h").val();

    cord_list= [W,H,X1,Y1];

    adj_list.push(cord_list);

  });

  jQuery("#save").click(function(){
    
    var val = adj_list;
    jQuery.ajax({
      type: "POST",
      url: "/image/save",
      data: {"cordinates": val},
      complete: function () {
      window.location.reload(true);
      }});
  });
});

</script>

ImageMagic Action :

Now we comes to the server side.I have created an action called save in my controller.Here the save action will accept the parameters, and then the magic comes with that snippet of ImageMagic as shown below.

def save
    cordinates = params["cordinates"]
    image_path = "# specify your image path "
    coordinates.each do |item|
       coordinate = item[1]
       cord = coordinate[0].to_s + 'x' + coordinate[1].to_s + '+' + coordinate[2].to_s + '+' +        coordinate[3].to_s

       system "convert #{img_path} -region #{cord} -fill white -colorize 100% #{img_path}"
    end
end.

The main keywords that you have to notice in the above snippet,is that "region" ,"fill" & "colorize".The "region" is nothing but the coordinates that we are sending via an ajax post request to the server.The coordinates are nothing but "Height","Width","X-cord","Y-cord".Here we are accepting that coordinates using params key word and assigning it to a variable .Then we have to specify the image_path of the desired image that you wants to hide."fill" keyword indicates nothing but the color that the user wants to hide with."Colorize" keyword is used to colorize the image by an amount that we specified.

Here we are iterating the loop and executing the command number of times equal to the number of selection."System" is the command in ruby to execute shell commands from the script.After executing the above script we will get the modified picture and then as a response we can send it to a client.But here in the Ajax post request i just put the command to reload the whole page again to affect the changes in the client side.Now the client will see the new image with the applied changes.

I have hosted this application in Heroku. Check out this,

http://magicalcoloring.herokuapp.com/

Ruby on Rails : Hosting your Ruby on Rails application in Heroku

2012-01-03T22:04:00.001-08:00

In my previous post,i have mentioned about creating a Ruby on Rails application using devise,Now in this tutorial we are going to host Ruby on Rails database backed application (Rails community web site) to Heroku.

you all know that Heroku is a polyglot cloud application platform. With Heroku, you don’t need to think about servers at all. You can write apps in the programming language of your choice, back it with add-on resources such as SQL and NoSQL databases.You can manage your app using the Heroku command-line tool and you deploy code using the Git revision control system, all running on the powerful Heroku infrastructure.

We have created our Rails community website application with a MySQL database support.The only problem that you have to face while hosting your application in Heroku is that Heroku doesn’t support MySQL , Heroku only supports PostgreSQL database for your application.

Sign up :

Before all, you have to create an account in Heroku,

Install the Heroku Toolbelt on your system :

If you are using a Ubuntu/Linux machine,follow the steps below.

$ apt-add-repository 'deb http://toolbelt.herokuapp.com/ubuntu ./'

$ curl http://toolbelt.herokuapp.com/apt/release.key | apt-key add -

$ apt-get update

$ apt-get install heroku-toolbelt

Login :

After installing the Toolbelt, you’ll have access to the heroku command from your command shell. Log in using the email address and password you used when creating your Heroku account:

$ heroku login

Enter your Heroku credentials.
Email: adam@example.com
Password:
Could not find an existing public key.
Would you like to generate one? [Yn]
Generating new SSH public key.
Uploading ssh public key /Users/adam/.ssh/id_rsa.pub

Install the Heroku Command-line Client :

Install the Heroku client by running the below command.

$ gem install heroku

Change the directory to where your application resides.

$ cd rails-club

Since Heroku doesnt support MySQL,You have to edit your gem file and the change the line

gem 'mysql2', '0.3.6'

to this,

gem 'pg'

Before that you should have to install the PostgreSQL in your system.

Once you have done all steps detailed above,then run the command “bundle install” to re-install your dependencies (to generate a new Gemfile.lock)

$ bundle install

Initialize git to store your application in git :

$ git init
$ git add .
$ git commit -m "init"

Deploy to Heroku/Cedar :

Create the app on the Cedar stack:

$ heroku create --stack cedar                                        
Creating fierce-fog-5356... done, stack is cedar
http://fierce-fog-5356.herokuapp.com/ | git@heroku.com:fierce-fog-5356.git
Git remote heroku added

Deploy your code:

$ git remote add heroku git@heroku.com:fierce-fog-5356.git

If you found an error reporting like,

fatal: remote heroku already exists.

run the following command,

$ git remote rm heroku

then you have to run the above command again.

$ git remote add heroku git@heroku.com:fierce-fog-5356.git

and finally run the following command to deploy your application in Heroku

$ git push heroku master

If the application hosted successfully in Heroku you will see something like

Launching... done, v5
       http://fierce-fog-5356.herokuapp.com deployed to Heroku

on your console.

After that you have to run the rake db:migrate command in Heroku, Rake can be run as an attached process exactly like the console.

$ heroku run rake db:migrate

copy and paste the Heroku application URL (“ http://fierce-fog-5356.herokuapp.com “) in your browser search bar.Now you have successfully hosted your Rails application in Heroku.

If you have just pushed to Heroku and want to make sure that you are up-to-date, just run,

$ git remote show heroku

then you will get output like this in your console.

* remote heroku
  Fetch URL: git@heroku.com:xxxx.git
  Push  URL: git@heroku.com:xxxx.git
  HEAD branch: master
  Remote branch:
    master tracked
  Local ref configured for 'git push':
    master pushes to master (up to date)

Ruby on Rails : Creating a simple Ruby on Rails application using Devise.

2012-01-03T05:01:00.000-08:00

If you have heard about rails and not yet experienced the power or features that , only rails can give ! this tutorial will help you to create Simple Ruby on Rails application without worrying too much about the syntax or working of Ruby on Rails.

Here in this tutorial we will create a database backed simple Rails community website application, so that all members can register and sign-in to the website.

About Rails :

Rails is a web development frame work written in ruby language,which has a general MVC ( Model, View, Controller ) architecture.Using a Rails framework will make everything effortless for the developers,who wants to build a powerful/fast application with a less set of code and rails will also help them to achieve more than any other framework can provide.

About Devise :

Simply Devise is a flexible authentication solution for Rails based on Warden. It:

Is Rack based.
Is a complete MVC solution based on Rails engines.
Allows you to have multiple roles (or models/scopes) signed in at the same time.
Is based on a modularity concept: use just what you really need.

Lets start coding:

We are going to create a simple rails community website with the help of devise,Before wr entering to our application you should have to gone through the basics of devise.please refer the following link if you want to learn more about devise and rails.

http://railsforzombies.org/ (one of the best tutorial session for Rails beginners )
https://github.com/plataformatec/devise
http://guides.rubyonrails.org/
http://railscasts.com/episodes/310-getting-started-with-rails

Installation :

I am using ubuntu 11.04, if you are using ubuntu you can follow the below link to install rails in your system.You can also install rails in windows or mac as well.

http://stuffingabout.blogspot.com/2011/04/installing-rails-3-on-ubuntu-1104.html

Creating your application :

Once you have installed every dependencies,you can start creating your first application in rails.

Use “rails new” command to create your application in rails,here we are going to create an application named rails-club.rails

$ rails new rails-club

$ cd rails-club

once you run the above command in your system, you can see that rails has generated so many files and folders inside your rails-club directory.

Editing the Gemfile :

We are going to create this application by using a devise, i have already told you that this is a database backed application.If you are using mysql as your database system then you have to edit your ‘Gemfile’ inside your rails-club directory and add the following line to your ‘Gemfile’.

$ gem 'mysql2', '0.3.6'

Once you have edited the Gemfile,please go through the files and directories the rails has generated,there is file called “database.yml “ in your “config” directory.Change theadapter to mysql2,and then specify your database,username and password . My “database.yml” file contains the following data.

Filepath : config/database.yml

development:
adapter: mysql2
encoding: utf8
reconnect: false
database: mydb
pool: 5
username: root
password: asdfgh

production:
adapter: mysql2
encoding: utf8
reconnect: false
database: mydb
pool: 5
username: root
password: asdfgh
socket: /var/run/mysqld/mysqld.sock

test:
adapter: mysql2
encoding: utf8
reconnect: false
database: mydb_testing
pool: 5
username: root
password: asdfgh
socket: /var/run/mysqld/mysqld.sock

Once you have done all the changes then run the “bundle install” command. This command tells “bundler”, a library used by Rails, to fetch and install all the libraries it needs.

$ bundle install

Installing Devise :

You can use the latest Rails 3 gem with the latest Devise gem, to install the Devise run the following command.

$ gem install devise

After you have installed Devise, you should have to specify the Devise gem to your Gemfile.

$ gem 'devise'

After that you need to run the generator by using the command below.

$ rails generate devise:install

The generator will install an initializer which describes ALL Devise’s configuration options and you MUST take a look at it. When you are done, you are ready to add Devise to any of your models using the generator.

Creating Models :

Here in this application we mainly needs 2 models,one is member model and the other one is contact model,the Member model should contain the member name, email, password, password confirmation etc.So now we are going to create our member model using devise.

$ rails generate devise member

This will create a model member and configure it with default Devise modules.And will also create some more files in your directory. The migration file will located in db/migrate/devise_create_members.rb.After that you should have to run db:migrate as the generator will have created a migration file.

$ rake db:migrate

== DeviseCreateMembers: migrating ==================================
-- create_table(:members)
-> 0.2575s
-- add_index(:members, :email, {:unique=>true})
-> 0.3146s
-- add_index(:members, :reset_password_token, {:unique=>true})
-> 0.4259s
== DeviseCreateMembers: migrated (0.9986s) =========================

Once you run the db:migrate command,rails will create a table called members with the following field that the Devise specified in the migration file.Check the tables has created successfully.

Now we have successfully generated our model.Just run the server by typing “rails server”.

$ rails server

=> Booting WEBrick
=> Rails 3.1.3 application starting in development on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
[2012-01-01 16:40:49] INFO WEBrick 1.3.1
[2012-01-01 16:40:49] INFO ruby 1.9.2 (2011-07-09) [i686-linux]
[2012-01-01 16:40:49] INFO WEBrick::HTTPServer#start: pid=5268 port=3000

copy and past the address http://0.0.0.0:3000/ to your browser search bar,you can see the rails home page .then you also try the following one. The Devise’s magic is comes here.

http://0.0.0.0:3000/members/sign_up

http://0.0.0.0:3000/members/sign_in

Here you could see that devise has generated the sign-up and sign-in forms for you.

Here the sign-up form contains only 3 fields email,password & password confirmation,No we have to add the username to the sign-up form.

run the following command to add the username field to members migration.

$ rails generate migration add_username_to_members username:string

This command will generate another migration file in your “db/migrate” directory.

And then again you have to run the “db:migrate” command.Then only the field will add to the members table.

$ rake db:migrate

== AddUsernameTomembers: migrating =================================
-- add_column(:members, :username, :string)
-> 0.3149s
== AddUsernameTomembers: migrated (0.3151s) ========================

Now you check the members table,username field will be added to it.

Creating Views :

Once you have done this you have to generate the Devise views,then only we can edit the sign-up form and add the username field to the form.

$ rails generate devise:views

Once you run this command the devise will generate the whole view files for the members.check “app/views/devise” ,you could see the whole form structure for sign-in,sign-up,forgot password etc.

Then edit the form for sign-up and add the username field to it.Go to“app/views/devise/registration/new.html.erb” and then edit the form like given below.

<h2>Sign up</h2>

<%= form_for(resource, :as => resource_name, :url => registration_path(resource_name)) do |f| %>

<%= devise_error_messages! %>

<div><%= f.label :username %><br />
<%= f.text_field :username %></div>

<div><%= f.label :email %><br />
<%= f.email_field :email %></div>

<div><%= f.label :password %><br />
<%= f.password_field :password %></div>

<div><%= f.label :password_confirmation %><br />
<%= f.password_field :password_confirmation %></div>

<div><%= f.submit "Sign up" %></div>
<% end %>

<%= render :partial => "devise/shared/links" %>

Now check the sign-up form again you can see the username field in it.

Lets create our second model Contact.Here we doesn’t use devise generator ,in contact model we need only 2 fields, phone number, address.

$ rails generate model contact

Edit the migration file of contact and specify the 2 fields as shown below.

class CreateContacts < ActiveRecord::Migration
    def up
        create_table :contacts do |t|
       
        t.string :mobile , :null => false, :default => “”
        t.string :address , :null => false, :default => “”

    end

end

    def down
        drop_table :contacts

    end
end

After that run db:migrate command to create a table contacts in our database.

$ rake db:migrate

== CreateContacts: migrating =======================================

-- create_table(:contacts)
-> 0.2141s
== CreateContacts: migrated (0.2142s) ==============================

Creating Controller :

We haven’t created an home page yet,so now we are going to create a controller for that.

$ rails generate controller home

And then create a new index file for home controller like “app/views/home/index.html.erb” and then add the following .

<% if member_signed_in? %>

<h3>you have succesfully signed in</h3>
<%= link_to "Sign Out", destroy_member_session_path, :method => :delete %>

<% else %>

<h1> welcom to rails community</h1>
<%= link_to "Sign In", new_member_session_path, :method => :get %>
<%= link_to "Sign up", new_member_registration_path, :method => :get %>

<% end %>

Once you have done ,you have to remove the index page in public folder,and then you should have to reset the root path to “home#index” page.

app/config/routes.rb

add the line

root :to =>'home#index'

Now we have to override the devise controller ,then only we can call the objects from 2 models (contact,members),so now we are going to create a new controller called “registration”.

$ rails generate controller registration

Open the controller file in “app/controllers/registration_controller.rb”,and then edit the file as shown below.

Filepath : app/controllers/registration_controller.rb

class RegistrationController < Devise::RegistrationsController

    def new

        @member= Member.new
        @contact = Contact.new

    end

    def create

        @member = Member.new
        @member.username = params[:member][:username]
        @member.email = params[:member][:email]
        @member.password = params[:member][:password]
        @member.password_confirmation =params[:member][:password_confirmation]

        @contact = Contact.new
        @contact.mobile = params[:contact][:mobile]
        @contact.address = params[:contact][:address]
        @member.valid?

        if @member.errors.blank?

            @member.save
            @contact.member = @member
            @contact.save
            redirect_to dashboard_path

        else
            render :action => "new"
        end
    end

end

Once you have done the above step,we are going to create a view for our registration controller, create file called “new.html.erb”,in your “app/views/registration/” directoryand then add the following.

Filepath : app/views/registration/new.html.erb

<h2>Sign up</h2>

<%= form_tag(member_registration_path,:method => 'post') %>
<%= devise_error_messages! %>
<table>

<tr>
<td>Username : </td>
<td><%=text_field_tag "member[username]",@member.username %></td>
</tr>

<tr>
<td>Email : </td>
<td><%=email_field_tag "member[email]",@member.email %></td>
</tr>

<tr>
<td>Password : </td>
<td><%=password_field_tag "member[password]",@member.password %></td>
</tr>

<tr>
<td>Retype password : </td>
<td><%=password_field_tag "member[password_confirmation]",@member.password_confirmation %></td>
</tr>

<tr>
<td>Mobile : </td>
<td><%=text_field_tag "contact[mobile]" ,@contact.mobile %></td>
</tr>

<tr>
<td>Address : </td>
<td><%=text_area_tag "contact[address]" ,@contact.address ,:rows => 10, :cols => 25 %></td>
</tr>

<tr>
<td><%= submit_tag nil, :class => "form_submit"%></td>
</tr>
</table>
<br />
<%= render :partial => "devise/shared/links" %>

We have to mention the relationships between 2 models (member ,contact ).here the relationship will be as follows.

Filepath : app/models/member.rb

class Member < ActiveRecord::Base

devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable

attr_accessible :email, :password, :password_confirmation, :remember_me, :username
has_one :contact
end

Filepath : app/models/contact.rb

class Contact < ActiveRecord::Base
    
   belongs_to :member
end

Now refer the registration controller file in app/controllers/registration,here after completing the registration & the values that the member entered is stored in the table successfully ,i just redirected the member to the dashboard page.So we have to add that page to our home controller.

Filepath : app/views/home/dashboard.html.erb

<p>hi welcome to Ruby community. you have successfully registered to your rails club account</p>
<%= link_to "Sign out", destroy_member_session_path, :method => :delete %>

You have to specify this path in our routes.rb file

Filepath : app/config/routes.rb

devise_for :members,:controllers => { :registrations =>'registration'}
match 'dashboard' => 'home#dashboard'

Conclusion :

Finally the application has almost done,so run the server and try our application in your machine whether everything working perfectly or not.This is just a skeleton of our application,we can add a lot more css to design our application to make everything looks perfect.

I hope that this tutorial will help you to start experiencing on Ruby on Rails application.If you facing any problems when you start trying out this application on your working environment,feel free to shoot your questions or suggestions. If you wants to get the fullcode of this application,please refer.

https://github.com/sreeharikmarar/simple-application-in-rails-using-devise

I have also uploaded this application in Heroku.Check out the following link.

http://railscommunity.herokuapp.com/

AJAX & Web.py : how to load a data from a server by using jQuery.get() method.

2011-10-22T08:51:00.000-07:00

We have already discussed some basic ideas about ajax and web.py in the previous post ,so now we are going to discuss some more functions that you can perform with ajax.

The Jquery.get() method is used to perform AJAX HTTP GET request.This is an easy way to send a simple GET request to a server.It allows a single callback function to be specified,that will be executed when the request is completed.

Syntax : jQuery.get ( url , [data] , [callback] , [type] )

url : The corresponding URL to load.
data : key/value pair that will be send to the sever (*optional).
callback : (Function) A function to be executed whenever the data is loaded successfully (*optional).
type : Type of data to be returned to callback function "xml","html","script","json" etc (*optional).

Now lets look at the working of JQuery.get() method here with the help of an example.

Qn: create a web.py URL that should return a random number between 1 & 1000,and create another URL it should display a text box and a button,when you hit the button,random numbers should be displayed inside the text box.

Before we are going to start You have to create a directory named static in the same folder where you are going to create this application.The HTML template will put in this directory.
First of all you all know that you have to map the URL's to the corresponding classes,here the root URL will map to 'rand_num' class and the second URL ('/random') will map to the 'return_num' class.

If we are using any HTML templates you have to define it by using the line 'render=web.template.render('template/'),then only it can fetch the code from the template directory,that why we already created a directory called template.

our web.py program displayed below.

program name : random.py

import web
import random

urls = (
    '/', 'rand_num',
    '/random','return_num')

app = web.application(urls, globals(), True)
render = web.template.render('templates/')


class rand_num:
    def GET(self):
      return render.random()

class return_num:
    def GET(self):
      return  random.randint(1,1000)

if __name__ == "__main__":
    app.run()

Then we have to define the class('/rand_num') for the root URL. the root URL should have to display a text box and a button,so that you have to call the corresponding HTML template ,here the method render.random() will returns a rendering of the HTML template 'random'.you have to specify the exact name of the html template that located in the templates directory here to fetch it from the directory when the code runs.

After that we have to define the class ('return_num') for the random number generation i.e when the browser get form this URL,it should return a random number between 1 - 1000 .We have a module in python called random ,by importing this module we can call random.randint() method to get random numbers between certain ranges,here we can use random.randint(1,1000) to get the random numbers between 1-1000.

Now lets look at the html template 'random.html' located in the templates directory.

<html>
        <head>
        <script type="text/javascript" src="http://ajax.microsoft.com/ajax/jquery/jquery-1.4.2.min.js"></script>
        
        <script type="text/javascript">
        jQuery(document).ready(function(){
        jQuery("button").click(function(){
          jQuery.get("/random",function(result){
             jQuery("#text1").val(result);
          });
        });});
        </script>
        </head>

        <body>

        <input type = "text" id = "text1" />

        <h2>Hit the button to view random numbers</h2>

        <button>Click</button>

        </body>
</html>

Here the url ("/random") specified in the jQuery.get() method specifies the corresponding url to load.and then the callback function specified here will execute when the data is loaded successfully.

Here when we press the button the jQuery.get() method will invoke and it will load the url "/random'.we have already defined the "return_num" class for the "/random" url that ,it returns only a random number between 1-1000.So when the data i.e (random number) is loaded successfully,then the callback function will execute and variable name "result" will contain the returned value.Then finally we just displayed it inside the text box.

Unix tool : make

2011-08-07T12:33:00.000-07:00

The make utility is a software engineering tool for managing and maintaining computer programs.Make provides most help when the program consists of many component files.

By creating a descriptor file containing dependency rules,macros and suffix rules,you can instruct make to automatically rebuild your program whenever one of the program's component files is modified.

To prepare to use make ,You must write a file called makefile the describes the relationships among files in your program,and the states the commands for updating each file.In a program,typically the executable file is updated from object files to decide which of the file needs to be updated.For each of those files,it issues the commands recorded in the data base.

Simple example:

This is an example descriptor file to build an executable file called prog1.it requires the source file file1.cc,file2.cc,and file3.cc.An include file mydefs.h,is required by files file1.cc and file2.cc.If you wanted to compile this file from the command line using C++ the command would be
% CC -o prog1 file1.cc file2.cc file3.cc

This command line is rather long to be entered many times as a program is developed and is prone to typing errors. A descriptor file could run the same command better by using the simple command

% make prog1

or if prog1 is the first target defined in the descriptor file

% make

No we are going to see how to write a descriptor file,this example descriptor file is much longer than the necessary but it is useful for describing what is gong on.

prog1 : file1.o file2.o file3.o
        CC -o prog1 file1.o file2.o file3.o
  
file1.o : file1.cc mydefs.h
        CC -c file1.cc
  
file2.o : file2.cc mydefs.h
        CC -c file2.cc
  
file3.o : file3.cc
        CC -c file3.cc
  
clean :
        rm file1.o file2.o file3.o

Let's go through the example to see what make does by executing with the command make prog1 and assuming the program has never been compiled.

Make finds the target prog1 and sees that it depends on the object files file1.o file2.o file3.o

make next looks to see if any of the three object files are listed as targets. They are so make looks at each target to see what it depends on. make sees that file1.o depends on the files file1.cc andmydefs.h.

Now make looks to see if either of these files are listed as targets and since they aren't it executes the commands given in file1.o's rule and compiles file1.cc to get the object file.

make looks at the targets file2.o and file3.o and compiles these object files in a similar fashion.

make now has all the object files required to make prog1 and does so by executing the commands in its rule.

Unix tool : AWK

2011-08-07T08:55:00.000-07:00

What is AWK?

AWK is a programming language designed for processing text-based data, either in files or data streams. It is an example of a programming language that extensively uses the string datatype, associative arrays , and regular expressions.

There are three variations of AWK:

AWK - the original from AT&T
NAWK - A newer, improved version from AT&T
GAWK - The Free Software foundation's version

AWK is an excellent filter and report writer.AWK also has string manipulation functions, so it can search for particular strings and modify the output.

The essential organization of an AWK program follows the form:

pattern { action }

The pattern specifies when the action is performed.i.e the pattern specifies a test that is performed with each line read as input. If the condition is true, then the action is taken.

Lets look some examples,First of all create a file named "file1.txt", and write somthing like "unix tool awk " in the body and then save,then type the following command in terminal

$awk '{print $1}' file1.txt

The output will be 'unix', i.e it will print the first word in the body of the file.
Two other important patterns can be specified by the keywords "BEGIN" and "END.",these two words specify actions to be taken before any lines are read.and after the last line is read.THe AWK program below:

  BEGIN ( print "START" )
   ( print )
  END ( print "STOP" )

We can make this into a typical AWK program :

Firt of create two files like "sample1.txt "with body " sam 15 groupA" & "sample2.txt" with body "neil 13 groupB" ,then write our AWK program as described below and save the file with extention (.awk) in the same directory that your sample file resides ,Here my awk program will be "file1.awk"

AWK is also an interpreter,Here we making the file executable by adding the first line in the beginning of the file i.e (" #!/bin/awk -f ").

programe name : file1.awk

#!/bin/awk -f

  BEGIN { print "Name\tAge\tGroup" }

  { print $1, "\t" ,$2, "\t" ,$3 }

  END { print " - DONE -" }

Then change the permission with the chmod command (i.e "chmod +x file1.awk" ),and then the script becomes a new command.Here the "-f" option following "#!/bin/awk" make the file execute directly i.e " awk -f file1.awk".

Then run the file by typing "$ awk -f file1.awk sample1.txt sample2.txt" in your terminal.then you will get the following output.

sreehari@~/sed awk make/awk09:54:02$ $awk -f file1.awk sample1.txt sample2.txt

    Name     Age   Group

    sam      15    groupA

    neil     13    groupB

    - DONE -

This is just a brief introduction to on AWK,You can find more about AWK by using the following document. AwK-Tutorial

Unix tool : Sed

2011-08-07T08:52:00.000-07:00

What is Sed?

This post will help you to get the answer of the above question,The same question persuaded me to understand the concept and also to write this post about what i have learned about Sed.

sed(stream editor) is a tool which allows you to perform large-scale, noninteractive editing tasks. For example, sed can replace all the occurrences of a given word in a file with a different word, or delete all lines containing a target string from a file.Sed is particularly used when working with large files .

Substitution command S:

Sed has several commands,but the essential command i.e used by most is substitute command : S

The substitute command changes all occurrences of the regular expression into a new value.

To try this command , create a file named "file1.txt" and write something like "sed is fun" in the body of that file,then run the following command in terminal.

$sed s/fun/cool/ <file1.txt >file2.txt

After you run the command you can see a new file created in the same directory with a name file2.txt , when you open the file you can see that the text is changed to "sed is cool".here the command will substitute the content "fun" in the old file (file1.txt) to "cool" in the new file (file2.txt).

Try the following command those who want to test the working in terminal.

$echo fun | sed s/fun/cool/

This will output as "cool" in terminal.

$echo sed is fun | sed 's/fun/cool/'

This will output as "sed is cool" in terminal.

There are four parts to this substitute command:

s Substitute command.

/ . . / . . / Delimiter.

fun Regular Expression Pattern Search Pattern

cool Replacement string.

The search pattern is on the left hand side and the replacement string is on the right hand side.

Using "&"as the matched string :

By using the "&" symbol you can match the patterns as you like,

$echo sed is fun | sed 's/[a-z][a-z][a-z]/(&)/'

This will ouput as " (sed) is fun ", [a-z] matches single letter ,here 3 [a-z] will match 3 letters like(sed).

You can have any number of "&" in the replacement string,like

$echo sed is fun | sed 's/[a-z][a-z][a-z]/(&&)/'

This will output as "(sedsed) is fun".

If you want to match the entire string then you have to make changes like,

$echo sed is fun | sed 's/[a-z]* [a-z]* [a-z]*/(&)/'

It will output as " (sed is fun)".

If you want to display the matched string 3 times then try,

$echo sed is fun | sed 's/[a-z]* [a-z]* [a-z]*/(&)(&)(&)/'

The output will be "(sed is fun)(sed is fun)(sed is fun)".

If we have a text file like "sed is fun 123",then you should change the code like this to get the whole text inside the bracket.

$echo "sed is fun 123" | sed 's/[a-z]* [a-z]* [a-z]* [0-9]*/(&)/'

Then the output will be "(sed is fun 123)".

Using \1 to keep part of the pattern:-

If you want to remove the numbers from the above example,then you should try like,

$echo sed is fun 123 | sed 's/$[a-z]* [a-z]* [a-z]*$.*/\1/'

It will remove the numbers and the output will be "sed is fun".

If you want to switch the words around, you can remember the patterns and change the order around:

$echo sed is fun 123 | sed 's/$[a-z]*$ $[a-z]*$ $[a-z]*$.*/\3 \2 \1/'

The output will be "fun is sed".

Substitute flags:

You can add additional flags after the last delimiter. These flags can specify what happens when there is more than one occurrence of a pattern on a single line, and what to do if a substitution is found.

$sed 's/[^ ]*/(&)/' <file1.txt>file2.txt

This will put parenthesis around the first word, i.e the first word in the body of your second file have a parenthesis around it.

If you want it to make change of every word add a "g" after the last delimiter and use the work-around:

$sed 's/[^ ]*/(&)/g' <file1.txt>file2.txt

The output will be "(sed) (is) (fun)".

These are some basic commands ,there are several other commands that can be used with Sed.

AJAX & web.py : some quick reference

2011-07-26T11:53:00.000-07:00

This post will give you some basic ideas about how to use AJAX with web.py.

You all know that web.py is a simple web framework for python,the main thing i liked about web.py is that it is very simple to use and more effective too.web.py frame work can run its own basic web server .

About AJAX(Asynchronous Java script and XML) you all know that it is very helpful to create interactive web applications.With Ajax, web applications can send data to, and retrieve data from, a server asynchronously , i.e you can updates the parts of web page without reloading the whole page.

So here i would like to describe some examples that we can experiment with AJAX & web.py.

The Ajax application that we are going to discuss here contain one "div" section and a button. The "div" section will be used to display the contents return form the server.

<html>
<body>
          
<div><h2>Let AJAX change this text</h2></div>
<button>Change Content</button>

</body>
</html>

With jQuery AJAX, you can request TXT, HTML, XML or JSON data from a remote server using both HTTP Get and HTTP Post.And you can load remote data directly into selected HTML elements of your web page!

Next, add a <script> tag to the page's head section. The script section contains the AJAX load function.The jQuery load() method is a simple AJAX function. It has the following syntax:

$(selector).load(url,data,callback)

Next we are adding the <script> tag under <head> section,This section contains jQuery load method.

<head>
      <script type="text/javascript" src="http://ajax.microsoft.com/ajax/jquery/jquery 1.4.2.min.js"></script>
      <script type="text/javascript">
      $(document).ready(function(){
        $("button").click(function(){
           $("div").load("http://127.0.0.1:8080/static/test.txt");    
        });
      });
      </script>
 </head>

Here the load function will load desired contents from the specified URL.(What this URL actually functions is described in the below section,you will get exact picture after you read the whole thing)

Next we are going to implement this code with web.py.

Before we move on to web.py,We have to create a folder named "static" in the same folder that your program resides,and put your text file (here the file is "test.txt" ) inside the "static" folder.Then check that you are able to access the file by typing the URL (" http://127.0.0.1:8080/static/test.txt ") in your browser search bar.If the browser displays the contents properly then you can implement this on aJax load function.

The whole program described below.

Program name -- Code.py

import web

  urls = (
    '/', 'main')


  app = web.application(urls, globals(),True)


  class main:
      def GET(self):
          return'''
          <html>
          <head>
          <script type="text/javascript" src="http://ajax.microsoft.com/ajax/jquery/jquery-1.4.2.min.js"></script>
          <script type="text/javascript">
          $(document).ready(function(){
            $("button").click(function(){
              $("div").load("http://127.0.0.1:8080/static/test.txt");
            });
          });

          </script>
          </head>
          <body>
            
          <div><h2>Let AJAX change this text</h2></div>
          <button>Change Content</button>

          </body>
          </html>'''


  if __name__ == "__main__":
      app.run()

How to run the program:

Web.py comes with a built-in web server that you all know. We have created our program file called " code.py ",just save the file and run the following command in terminal to start your application.

sreehari@sreehari-desktop:~/web.py$ python code.py
  http://0.0.0.0:8080/

Then goto your browser and type " http://127.0.0.1:8080/ " in your search bar , you will get a web page with a text " Let AJAX change this text " and it also contains a button,when you hit the button the text will change and new text from the text file will be loaded and displayed in your browser.

A simple exercise in web.py

2011-07-18T04:26:00.000-07:00

This is just a simple exercise that will help you to understand the basics of web.py.

Qn: Create a webpage that should contain a text box,so that you can input your names,the page should also provide a submit button to submit the details that you entered in a text box.when you submit it the names should be saved in a text file and whole the names that we entered should be displayed in another URL.

1st step: Import the module Web.py,to use the tools provided by web.py. Map the first URL (" / ") to a class named "main".and map the second URL ("/Details") to a class named "details".

import web

  urls = (
    '/','main',
    '/Details','details')

  app = web.application(urls, globals(), True)

2nd step: Next we have to define the class named "main".The function GET() is actually displays the content in your browser when you opens a webpage.When you opens the first page it should displays a form,so thats why ,we are writing the HTML code to create a form under GET() function.Here we are specifying the method attribute of form as POST to invoke the POST request .

class main:
    def GET(self):
    return'''
    <html>
    <head>
    <title>web.py</title>
    </head>

    <body>

    <h1>A simple exercise in web.py</h1>

    <form name="form" method = "POST">

    Name: <input type="text" name="user"/>

    <input type="submit" value="Submit" />

    </form>
    </body>
    </html>'''

3rd step: The GET() function that we introduced above will only serve the pages ,but here we have to update the values to another webpage.Thats why we are using a POST function.The line "form = web.input()" creates a storage objects that contains all variables passed into it.Then we open a file named "file.txt" in append mode,then write the input values into the file by using " f.write(form.user) ". Then Web.redirect('/Details') will redirect the user to a new URL(" /Details ") ,i.e when we submit the form it will guide you to the next page that contain all the details that you entered before.

def POST(self):

   form =  web.input()
   f=open("file.txt",'a')
   f.write(form.user)
   f.write("\n")
   f.close()

   raise web.redirect('/Details')

4th step: We have to define the class for the URL("/Define").Here we are using GET() function to display the contents.so to displays the contents in the text file we just simply opens the file in read mode.and then read the values by using "f.read()" function and then assigned it to a variable named data,when we return the variable it will displays all the values that we read from the text file in the next URL.

class details:

  def GET(self):

    f=open("file.txt",'r')
    data=f.read()
    return data
    f.close()

Complete code:

Program name: Code.py

import web

urls = (
  '/','main',
  '/Details','details')

app = web.application(urls, globals(), True)

class main:
   def GET(self):
    return'''
    <html>
    <head>
    <title>web.py</title>
    </head>

    <body>

    <h1>A simple exercise in web.py</h1>

    <form name="form" method = "POST">

    Name: <input type="text" name="user"/>

    <input type="submit" value="Submit" />

    </form>
    </body>
    </html>'''

    def POST(self):
 
      form =  web.input()
      f=open("file.txt",'a')
      f.write(form.user)
      f.write("\n")
      f.close()

    
      raise web.redirect('/Details')
    
class details:
    
    def GET(self):

      f=open("file.txt",'r')
      data=f.read()
      return data
      f.close()

if __name__ == "__main__":
    app.run()

Web.py : Installation and working

2011-07-10T13:14:00.000-07:00

Web.py is a simple web frame work that is written in python for the development of python related web applications.The main feature about web .py is that it is very simple and efficient compared to others

Installation:-

Download web.py from the below link.Then extract and copy it into to any directory that your application resides or make it accessible to all applications.

http://webpy.org/static/web.py-0.36.tar.gz

Type "cd" in Terminal to "change the directory "where you copied web.py, If you list the contents you can see a setup.py file inside it. To install the file type the below command.

python setup.py install.

when you found any permission denied messages when installing in unix like systems,switch to root user and then try the below command.

sudo python setup.py install

Working:-

when you installed it properly you can try it by creating some simple webpages.Open any of your favorite editor and creating a file named "hello.py" as shown below.

import web

urls = (

'/', 'hello')

app = web.application(urls, globals())

class hello:

def GET(self):

return 'Hello, web!'

if __name__ == "__main__":

app.run()

Here first you need to import the module web.py to use the tools provided by web.py i.e the first line actually refers.

In the second line we are actually mapping the web address(URL) i.e "http://webpy.org/" to a python class named "hello".

Inside the class you can see a function named "GET()".This function "GET()" is actually displays the content in your browser when your browser opens a web page.Here it will display the string "Hello,web" .

In the third line we are creating an instance .It will handle the all duties like handling the browser request and serving the desired pages.

The last line will start the web application to handle your requests.

Save the above file and run by using the command python hello.py.

when you run the file,the output will be the address of your website ,by default it is (http://localhost:8080/). when you copy it and paste it in your browser search bar you will get the resultant web page.

Python : Interesting String & List

2011-06-28T09:27:00.000-07:00

Here i would like to share some interesting behavior of String & List when you use python interpreter.

String:-

We all know that the fundamental thing about Python Strings is that they are "Immutable" ,once you created a string you couldn't change it. See some examples....

>>> s = 'fun with string'
>>> s
'fun with string'
>>>

you can just add another string by using '+' as shown below...

>>> s + '!!!!'

'fun with string!!!!'

>>>

Another important feature is String Slices. Just see how "slice" syntax behaves in python.

>>> s = 'fun with string'

>>> s[0]

'f'

>>> s[1:4]

'un '

>>> s[1:]

'un with string'

>>> s[:]

'fun with string'

>>> s[-1]

'g'

>>> s[-4]

'r'

>>> s[:-3]

'fun with str'

>>> s[-3:]

'ing'

>>>

So now we have a string 's' and we can apply all the methods (i.e functions) that are related to string to 's' as shown below...

>>> s.upper()

'FUN WITH STRING'

>>> s.lower()

'fun with string'

>>> s.startswith('fun')

True

>>> s.endswith('string')

True

>>> s.replace('string','python')

'fun with python'

>>>

But my favorite is the method called ' s.split() '. Just see what happens if i assigned s.split() function in to a variable 's' itself. If we print it you can see a list of elements.It just transformed into a list.

>>> s = s.split()

>>> s

['fun', 'with', 'string']

>>>

List:-

So now the variable 's' will behave like a list.Now you can apply all the methods related to list here with 's'.

>>> s.append('& list')

>>> s

['fun', 'with', 'string', '& list']

>>> s.insert(0,'some')

>>> s

['some', 'fun', 'with', 'string', '& list']

>>> s.index('some')

>>> s.index('string')

>>> s.sort()

>>> s

['& list', 'fun', 'some', 'string', 'with']

>>> s.pop(0)

'& list'

>>>

See what happens if i call the function " join() ",and assigned it to same variable 's' .When you print 's' you could see the first string.Is it interesting?

>>> s = ['fun', 'with', 'string', '& list']
>>> s = ' '.join(s)
>>> s

'fun with string & list'

>>>

Thank You....

Unix to Linux story

2011-06-24T22:33:00.000-07:00

The story has begun from the well known AT&T’s Bell Laboratories in the early 1960 ’s.

At that time AT&T needed an operating system for their computer center because they were running various batch jobs .The BESYS operating system was created for at Bell Labs to deal with these needs. so at the year of 1965 Bell Labs was adopting third generation computer equipment and decided to join with General Electric and MIT to create a Multics (Multiplexed information and Computer service).But at the year of 1969 they made a change that ,to withdraw from Multics and go with GECOS.

When Multics was withdrawn Ken Thompson and Dennis Ritchie needed to rewrite the operating system, And finally they made a system called UNICS (UNiplexed Information and Computing Service) ,

The UNIX operating system was first developed in Assembly language but , by the year of 1973 it had been almost entirely recoded in C. The first edition of the UNIX Programmers Manual includes over 60 commands like : b , boot , cat , chdir , chmod , cp , ls , mv etc.

Second edition of UNIX was released in 1972.But now you all know that it has been split in to various branches developed by AT&T for various commercial purposes.

AT&T made UNIX available to Universities and commercial firms as well as the United States government, under licenses. The licenses include all source code including the machine dependent parts of the kernel. The copies of the UNIX kernel sources circulated widely in late 1970s in the form of much copied Book by John lions of the University of new south Wales.

Intel created the first commercially available microprocessor (Intel 4004) in 1971, and one of the first microcomputers in 1972.They emerged from versions to versions like 80386.80486,80586 etc. Pentium i.e Intel 80586 was introduced in 1993.They mainly focused on making it useful for the ordinary people.

At the year of 1975 the software is emerged as an independent entity. Companies like HP and SUN started to using UNIX as an operating system for their machines. HP-UX 1.0 is released in 1980.SUN unveils Solaris 2 Operating system, specially tuned for symmetric multiprogramming at the year of 1991

AT&T Licensed UNIX system III , and continued to issue license for the older versions . So to end the confusion between all its versions , AT&T combined them into UNIX System V release 1.This introduced a few features like vi editor and courses from the Berkeley Software Distribution of Unix developed at the University of California, Berkeley

This move of AT&T , that to commercialize UNIX system v .actually killed UNIX. The Free Software Foundation (FSF) was founded the same year by Richard Stallman.

Richard Stallman’s contribution

Richard Mathew Satallman (rms),was against the U.S Copy write Act ,i.e restricting the unlicensed access to the software. Stallman proclaimed it and argued that it is blocking the user’s freedom to use it.In 1984 he quit his job from MIT to work full time on GNU project.

The main intention behind GNU Project is to create free Unix-like operating system. With the launch of the GNU Project he founded the Free Software Foundation(FSF).

Stallman popularize the concept of Copyleft ,a legal mechanism to protect the modification and redistribution rights for free software. In 1989 the first program independent GNU General Public License (GPL) was released.

The GNU system was almost completed by then,he was contributing many naccessary features like Text editor (Emacs), Compiler (GCC) , Debugger (gdb).But one important thing was missing , i.e Kernel. The GNU kernel ,called Hurd ,failed to attract enough attention from developers leaving GNU incomplete.

Linus Torwalds donated the kernel.The existing programs for the GNU projects were ported to run in the new platform. and then formed the GNU/LINUX projects.

Linus Torvalds’s contribution

When he was studied at Helsinki, he began a project that later becomes the Linux kernel.The main intention behind the project was to write a program specifically for the hardware that he was using and that should function independent of an operating system.

The development was done on MINIX operating system,using the GNU C Compiler. He wrote on his book that he eventually realized that he had written an operating system, and he made a post in Usenet,that “ I am doing a (free) operating system, I’d like any feedback on things people like/dislike on MINIX…”

He made it successful,and the first version of Linux has released.He first published the Linux kernel under its own license, but later licensed under GNU General Public License(GPL). In the first release of Linux 0.01 Torwalds lists the GNU software that is required to run Linux.

Now Linux has many versions and distributions,and proves itself as one of the worthy opponent to Windows giants.Many IT industries are now started to use Linux as a better alternative.

Thank You..

Python : Script mode

2011-06-20T11:46:00.000-07:00

We have already discussed that python is an interpreted language and mainly there are two ways to use the interpreter , i.e Interactive mode & Script modes . In the interactive mode it just displays the result of expressions , We can have the python interpreter to execute our script file also.

In script mode we can store the code in a file and use the interpreter to execute the content of the file which we called a script.The scripts must have saved with the extension .py.

To edit the scripts, you can have common editors like gedit , VIM ,eric4 and eric5 etc , Several type of editors are available for Unix and Windows.

But when you edit python scripts the indentation must be accurate, In all our files we use 2-spaces as the indent and 4-spaces is another popular choice.

Script mode

There are several ways to use the interpreter and have execute our scripts.

Explicit Command line execution:

Here python script is executed by providing the script file name as parameter to the python interpreter.In this style we explicitly name both the interpreter and the input script.

we have a sample python script file called sample.py is shown below.When you type python sample.py ,it will provide sample.py file to the python interpreter for execution.

You could see an import statement on top of the program ,by using this syntax you can pass command line arguments,i.e sys.argv[1] will print the argument that you passed along with the file name.
if __name__ == '__main__' is the boilerplate syntax to call the function main().It is mainly used when a python file is run directly.

Output of the following program is displayed below .

Implicit command line execution:

We can make the script file itself executable and directing the shell to locate the python interpreter.For windows we can associate our script file .py with python.exe .There are one or two steps to do this.

when you creating a script file make sure that first line of the file contain the following #!/usr/bin/env python.

If you enter the above code, the whole file will look as follows.

For POSIX-standard operating systems,do chmod +x sample2.py to make the file sample2.py executable.
Then you can run the file by using ./sample2.py command.

when you run the file ,you will get the expected output as follows.

Thank You..

Project on ExpEYES

2011-04-28T22:18:00.000-07:00

A FRAME WORK FOR CONTROLLING expEYES (Brief)

expEYES is from the PHOENIX project of Inter-University Accelerator Centre, New Delhi. It is a hardware & software framework for developing science experiments, demonstrations and projects and learn science and engineering by exploration. Capable of doing real time measurements and analysing the data in different ways. Analog voltages, in +/- 5 volts range, are measured with 12 bit resolution (around 1.25 millivolts) and time intervals with one microsecond.

This project is based on Free and Open Source software, mostly written in Python programming language. The hardware design is also open. A science laboratory at home becomes an affordable idea, with expEYES, costing around Rs.3000/- and the stuctured design supports adding more experiments without much effort.

The expEYES hardware is interfaced and powered by USB, having a size of 11 x 9 x 1.5 cm and weighs 150 gm. There are 32 terminals arranged in two rows where you can connect external signals, within +/-5 volts range, for control and measurement. It can function as a signal generator, frequency counter and low frequency oscilloscope .

I actually planning to do this project with the support of online functionality.i.e you can control any devices that you already connected with these expeEYES through web.Here i use Javascrpt/HTML as my Front-end support and Python would be the back-end.

Here you could connect several other devices with this expEYES , and can do several experiments with the support of expEYES.The accessory set that could connect with this expEYES is shown below.

The communication with the expEYES is done using a library written in Python language.Programs with GUI have been written for many experiments.They will run on any computer having a Python interpreter and a Python module to access the USB port.

Debian packages are available for Debian and Ubuntu GNU/Linux distributions.

Further updates about this experiment will publish soon......

Will see you ..