vadivelan ruby on rails blog

Solr

2011-10-20T02:26:00.000-07:00

Integrating SOLR search into our application. “acts_as_solr” is the name of the plugin(also available as gem).
Install plugin:

script/plugin install git://github.com/mattmatt/acts_as_solr.git

Install gem:

gem install acts_as_solr

Add the below line into your application's configuration file

config.gem "acts_as_solr"

Add this at the end of your Rakefile(only for using gem)

require 'aas_tasks'

After installing gem/plugin, following rake tasks are available to use
rake solr:destroy_index # Remove Solr index
rake solr:reindex # Reindexes data for all ac
ts_as_solr models.
rake solr:start # Starts Solr.
rake solr:stop # Stops Solr.
We can start, stop, reindex, destroy index by using the mentioned rake tasks.

Add the following rake task inside the solr rake file(gems/acts_as_solr/lib/tasks/solr.rake), to start solr in Windows environment.

desc "Starts Solr. on windows . Options accepted: RAILS_ENV=your_env, PORT=XX. Defaults to development if none."
  task :start_win do
    require "#{File.dirname(__FILE__)}/../../config/solr_environment.rb"
    begin
      n = Net::HTTP.new('localhost', SOLR_PORT)
      n.request_head('/').value

    rescue Net::HTTPServerException #responding
      puts "Port #{SOLR_PORT} in use" and return

    rescue Errno::ECONNREFUSED #not responding
      Dir.chdir(SOLR_PATH) do
        exec "java -Dsolr.data.dir=solr/data/#{ENV['RAILS_ENV']} -Djetty.port=#{SOLR_PORT} -jar start.jar"
        sleep(5)
        puts "#{ENV['RAILS_ENV']} Solr started sucessfuly on #{SOLR_PORT}, pid: #{pid}."
      end
    end
  end

Steps to configure solr in our application

1) Starts the solr server

rake solr:start

2) Changes to ActiveRecord model
acts_as_solr - all fields are indexed

class News < ActiveRecord::Base
     acts_as_solr :fields => [:title, :content] 
   end

– specified fields are indexed
We can specify the name of the fields to be used for searching.
Options:
:if => we can supply any condition as string, proc, symbol, method. It will index the record only if condition returns true.

3) Do index/reindex

rake solr:reindex

4) Changes to Controller

News.find_by_solr(query)

query => query is a string representing your query

There are many options available in solr, we can do a refined search by using SOLR.

Problem:
I faced one problem, acts_as_solr :if option is not working with rake task to reindex data. Instead of checking the condition it will simply indexes all the records. But other method like solr_save() checks the condition passed with acts_as_solr definition in model. I have added a patch to check the condition in rake task 'reindex'.

file path: acts_as_solr\lib\class_methods.rb
line no: 200 - 250
method name: rebuild_solr_index
Instead of normal collect,

items.collect! { |content| content.to_solr_doc }

We can use the following code, to filter the records with the condition defined in model and collect the remaining results

items = items.select { |content| content.evaluate_condition_public(content)}
items.collect! { |content| content.to_solr_doc }

After doing the above changes, you can have a correct data in your search results. This is applicable only when we are using acts_as_solr with conditions in model.

acts_as_solr :fields => ["name","description"], :if => proc{|record| record.active?}

Hope, this is useful for someone who is using acts_as_solr with :if option.

Cheers,
Vadivelan

Functional Testing in Rails(to test Html)

2011-08-18T04:18:00.000-07:00

Hi all,

I have used listed out some uses of assert_tag in Rails functional test. In many case, we need to test the html content of page like checkbox is checked or not, text fields holds correct value, drop down selected with correct option. For those kind of needs, we need to go for assert_tag. Below are the example usage of assert_tag in functional testing.

In Rails html testing, assert_tag method plays an vital role. Following are some of the ways to use assert_tag method

Get links inside div

assert_select "div#divID" do
assert_select "a[href=?]", "/path/to/some/page"
end

Check the content of any html element(here is an example for Div)

by className
assert_select "div.className", "Page Heading or content inside the div"
by element ID
assert_select "div#elementId", "Page Heading or content inside the div"

Check how many times any DOM element appears on the page:

In the below example, we tested how many number of user images loaded on the page
assert_select "div.className table tr td.userImage img", {:count => 4}

Presence of Textbox:

assert_tag "input", :attributes => {:id => "user_screen_name", :size => "30", :type => "text"}

Get value of Dropdown:

option = css_select("select#elementId option[selected='selected']")[0]
assert_equal "public", option['value'].to_s

Code with testcase improves the quality of code and at the sametime reduces the errors. Keep writing test for each line of code.

Alternative to "grep" command in Windows

2011-04-18T06:41:00.000-07:00

Hi all,

I have shifted from ubuntu and started using windowsXP. When I tried to use the grep command in windows, it throws the error

Instead of using grep, we can use find

gem list|find "rails"

rails (3.0.10)

Cheers,
Vadivelan

Month with number of count display for any model in your application

2011-02-02T01:27:00.000-08:00

By using rails finder method, it is very easy to display the number of post and month accordingly.
Here is the query

>> Post.count(:order => 'DATE(created_at) DESC', :group => ["DATE_FORMAT(created_at,'%m/%Y')"])
=> #< OrderedHash {"06/2010"=>1, "03/2010"=>1, "02/2010"=>1}>

Result is a collection hash ordered in the form of latest month as first one, Collection contains the month as Key and number of count as Value.

If we run it through the each loop and it is very easy to display.

Thanks,
Vadivelan

Ruby keywords

2011-01-10T00:47:00.000-08:00

List of ruby keywords

1. alias
2. and
3. BEGIN
4. begin
5. break
6. case
7. class
8. def
9. defined
10. do
11. else
12. elsif
13. END
14. end
15. ensure
16. false
17. for
18. if
19. in
20. module
21. next
22. nil
23. not
24. or
25. redo
26. rescue
27. retry
28. return
29. self
30. super
31. then
32. true
33. undef
34. unless
35. until
36. when
37. while
38. yield

SQL order_by "field" option

2011-01-09T23:32:00.000-08:00

Hi all,

I tried to order the SQL results in a pre-defined order. Consider the case

Am having users table, and a field called 'status' to store the current status of the user.
In back-end of my site, am displaying all the users with order-by 'status'

Possible status values are "Pending", "Approved", "Canceled", "Deleted"

I need to display users in the following orders,
"Approved", "Pending", "Canceled", "Deleted"

The normal order by field orders the field in either ASC/DESC. But in this case it is different.
For this i used the following query to fetch SQL results in a defined order

Rails finder:
User.find_by_sql("select * from users order by field (status,'Approved', 'Pending', 'Canceled', 'Deleted')")

SQL query:
select * from users order by field (status,'Approved', 'Pending', 'Canceled', 'Deleted');

Result contains the collection in the defined order.

When you are using this "order by field" option, you have to give all the option in the order then only it will works.

Thanks,
Vadivelan

ActiveRecord::Base increment & decrement method

2010-11-10T19:28:00.000-08:00

Hi all,

Yesterday while i was working in a task, i need to increase the points of an user. For that i have used the update_attribute method like below

user = User.last
user.update_attribute(:points, 5)

Then i found the active record base in-built method called "increment" and "decrement". So i used the following method to increment/decrement the user points.

user.increment(:points) # it will increase points by 1(default increment count) and returns the user object(self)
user.save
user.increment!(:points) # and this one will do the above two operations i.e., assigns the value to the attribute and saves the record. It will returns true or false(validation result).

user.increment(:points, 5) # we can pass the value like this to increment the attribute by this much. Here points will increases by 5
user.save
user.increment!(:points, 5)

The same is applicable to the "decrement" method, syntax is given below
user.decrement(:points)
user.decrement!(:points)
user.decrement(:points, 5)
user.decrement!(:points, 5)

Thanks,
Vadivelan

Use of rails console

2010-10-06T21:52:00.000-07:00

Hi all,

We can use our rails console(powerful tool for rails app) for debugging and testing. Mainly console helps us to learn more about Ruby

Normally we are using console to talk with our database, and fetch the objects from db.
ex:
User.first
User.all

But apart from that we can use our console to interact with our application using the object "app"
"app"

app.class # returns this
ActionController::Integration::Session

we can fire(get/post) requests to our application from console itself.

>> app.get "/login"
=> 200
it returns the status code for the handled request

>> app.post "/user_sessions", :user_session => {:email => 'vadivelan@example.com', :password => 'secret'}
=> 302
we can send post request with parameters like this

>> app.response.redirect?
=> true
redirected to some other url

>> app.response.redirect_url
=> "http://localhost/login"
view the redirect url

Hope now you guys can start firing the requests to application from console.

Thanks,
Vadivelan

ruby send method

2010-09-24T04:56:00.000-07:00

Hi all

I am started using the method named "send".

We can use this to call the method using object.

class User

def say_hello
"Hello"
end

end

u = User.new
puts u.send(:say_hello)

Here the class "User" is having the method called say_hello. We can create an object for the user class and call the method using the method "send"

Cheers,
vadivelan

ruby extend method

2010-09-21T11:14:00.000-07:00

Hi all,

I have seen the method named "extend" used in a line of code in Plugin. Then i started searching for the use of method "extend". And i found the following

consider the example

module Friend
def say_hello
"hello am inside module"
end
end

class Person
def say_hello
"hello am inside class"
end
end

p = Person.new
puts p.say_hello #=> hello am inside class

p.extend(Friend) #=> include all the instance method from Module "Friend"
puts p.say_hello #=> hello am inside module

So the extend method is used to include the Module.
Without this we cannot call the method inside the module using the Person object. Even if i added include the module in the class, it wont calls the module method. The instance method inside the class gets called for the object(Person class).

Use of Proc & proc

2010-09-15T23:54:00.000-07:00

Hi

I have used "proc" to run/block validation in model. But now i learned something more about proc.
In ruby, "Proc"(procedure) refers to the block of code, we can reuse it. Block of code assigned to the object.

"Proc" => Starts with capital letter refers to (class name)
"proc" => Refers to the proc object

We can use both the keywords to create a proc by defining any block to them.

below sample code to create a proc and call that proc to execute the block of code

accepts_any_arg = Proc.new{ |a,b,c|
puts "#{a} #{b} #{c}"
}
accepts_any_arg.call(1)
result: 1
accepts_any_arg.call(1,2)
result: 1 2
It just neglects the number of arguments required or passing to that proc, it is working without any argument error. It assigns nil value to arguments which are not passed.

throws_args_error = proc{ |a,b,c|
puts "#{a} #{b} #{c}"
}
throws_args_error.call(1,2,3)
result: 1 2 3
throws_args_error.call(1)
result: Throws "ArgumentError"
it is checking the number of arguments

Thanks,
Vadivelan

Ruby - "defined?" method

2010-07-22T08:10:00.001-07:00

Hi all,

In ruby we are having many methods to check whether the variable defined or not. Mostly we are using the following condition to check the variable defined or not

Code:
if local_variable
puts "local variable exists"
else
puts "local_variable does not exists"
end

But there is another way to check the variable defined or not.

sample-code:

a = 10
puts defined?(a).inspect => "local-variable"
puts defined?(b).inspect => nil

So, the method returns the value "local-variable" for the already defined variables and "nil" for the undefined variables.

Hope hereafter you guys using the method "defined?" to check the variable already defined or not.

Cheers,
Vadivelan

ruby math functions

2010-05-24T20:54:00.000-07:00

Hi all,

Here i have listed some of the most frequently used math functions in ruby.

round method rounds the value
if decimal value is less than .5, rounded to its lowest value
irb(main):006:0> 1.2.round
=> 1
if decimal value is greater than .4, rounded to its highest value
irb(main):007:0> 1.5.round
=> 2

floor method rounded the value to lowest value
irb(main):008:0> 1.5.floor
=> 1

ceil method rounded the value to next highest value
irb(main):009:0> 1.5.ceil
=> 2

'nan' method used to check whether the value is integer or not
irb(main):010:0> x = 0.0/0.0
=> NaN

irb(main):011:0> x.nan?
=> true

Get ASCII value
irb(main):017:0> Integer(?e)
=> 101

irb(main):018:0> Float(?e)
=> 101.0

>> "%.2f" % (1.0/2.0)
=> "0.50"

The last method is mainly used for display purpose. We have to display the floating point number in any page(say to display the cost) we must modify the output in such a way to get clear display(Max of 2 numbers after decimal point in this case).

Thanks,
Vadivelan

Some more uses of '$' in prototype javascript

2010-05-24T20:45:00.000-07:00

Hi all,

We are all using the '$' in prototype javascript to get the object of the matched DOM element by using id of the element.

Say for example:

the page has the div element

content inside the div element

To get the object of the div element we are using the '$'.

$('container') => returns the object of the DOM element.

$A/$W/$F => are also available but rarely used..

the below lines explain the use of the $A/$W/$F

// converts a string into array, each element is taken as a count
>>> $A('1')
['1']
>>> $A('123')
["1", "2", "3"]

// converts a string into array, it takes whitespace as delimiters
>>> $w('1 2 3')
["1", "2", "3"]

// used to get values of text field which is located inside any forms
// same as Form.Element.getValue
>>> $F('press_room_url')

So start using these commands makes the code simpler..

Thanks,
Vadivelan

jQuery with rails

2010-03-31T21:48:00.000-07:00

Hi all,

I have used the jquery js prototype recently, it has lots of more usage than our prototype.js. Easy to code using jQuery.js.

But in my rails application i have used both prototype.js & jquery.js. In this situation the $ gets conflict. To avoid conflict, use the line of code

First include prototype.js, then add jQuery.js after that you must add this line to avoid ($)conflict

Once you done this, you can enjoy the usage of both prototype.js & jQuery.js.

i.e., both $ and $j is available to access.

$('id_of_dom_elemnt') => returns (prototype)object of the html element
$j('#id_of_dom_element') => return (jquery)object of the html element

In jQuery, we have to add '#' symbol with id of dom element to find the element.

Enjoy coding with jQuery...

thanks,

JSON startup

2010-01-23T02:04:00.000-08:00

JSON - javascript object notation

To know about the JSON, first go through the following basics in js.

Array:

var arr = new Array("first", "second", "third", "fourth");

Retrieve value from array

arr[0] => "first"
arr[1] => "second"

Object:

var sample_object = {
"name1" : "value1",
"name2" : "value2",
"name3" : "value3",
"name4" : "value4"
}

sample_object.name1 => "value1"
sample_object["name1"] => "value1"

Objects in Array

var object_array = [
{
"first_element" : "first_value"
},
{
"second_element" : "second_value"
}
]
object_array[0] => returns first object
object_array[1].second_element => second object value

Arrays in Object:

var sample_object = {
"name1" : "value1",
"name4" : [1,2,3,4]
}
sample_object.name4 => [1,2,3,4]
sample_object.name4[0] => 1

var str_json = JSON.stringify(sample_object);
var js_object = JSON.parse(str_json);
JSON.parse(strJSON) - converts a JSON string into a JavaScript object.
JSON.stringify(objJSON) - converts a JavaScript object into a JSON string.

Watir tips

2009-12-07T18:33:00.000-08:00

Hi Guys,

Waitr is a ruby gem used in testing. It has many uses, mostly it is used to control the web browser(all html dom elements as objects).

installation command:-
gem install waitr

Some sample use of watir

1. Starting a new Web browser
require 'watir'
ie = Watir::Browser.new
ie.goto("http://www.google.com")

2. Starting a firefox browser
require 'watir'
Watir::Browser.default = "firefox"
ff = Watir::Browser.start("http://www.google.com")

3.Setting a text field with some value

ie.text_field(:name, "username").set "Vaddi"

4. Setting value of select list

ie.select_list( :name , "category").select("Comedy")

For all the DOM elements, it has objects(for text box - 'text_field', for drop down - 'select_list')

thanks,

for loop - js

2009-12-04T18:46:00.000-08:00

In javascript, to read the array index and their appropriate value.

Use the following way,

var a = Array.new(); declare new array with name 'a'
a = [1,2,3,4,5]; assign some values to array
var indexes = function show(value, indx){
alert(indx);
alert(value);
}
a.forEach(indexes);
'forEach' method is used to collect the values from the array.

By using the method 'forEach', we can collect each element from array.

Try this..

Add favicon image to your site

2009-11-30T01:06:00.000-08:00

Its very easy to add favicon to ur site by following steps

include the line in your layout head
html link tag
with attributes
rel="icon" href="favicon_path"
type="image/x-icon"

favicon_path = image path of favicon

That's it...

Try with this..

has_many_friends association

2009-11-27T03:54:00.000-08:00

Hi Guys,

I have stuck while building the association for model user,
user has_many friends, friend - nothing but a user

For that i have created a model called 'Friendship', user to join user and friends. And build the association with the following relations

friendship table has the following fields
user_id
friend_id

class User < ActiveRecord::Base
has_many :friendships
has_many :friendships_by_me, :foreign_key => 'user_id', :class_name => 'Friendship'
has_many :friends_by_me, :through => :friendships_by_me, :source => :friendshipped_by_me
has_many :friendships_for_me, :foreign_key => 'friend_id', :class_name => 'Friendship'
has_many :friends_for_me, :through => :friendships_for_me, :source => :friendshipped_for_me
end

class Friendship < ActiveRecord::Base
belongs_to :user
belongs_to :friendshipped_for_me, :class_name => "User", :foreign_key => 'user_id'
belongs_to :friendshipped_by_me, :class_name => "User", :foreign_key => 'friend_id'
end

Thats it!!!

Now run the following commands

user = User.first
user.friends_by_me => [users] returns the collection of friends added by user.
user.friends_for_me => [users] returns the collection of friends who add user as their friend.

Note: i have referred the plugin 'has_many_friends'.

Thanks,
vaddi

Drop down methods

2009-11-15T22:16:00.000-08:00

java script methods for drop down.

selectedIndex - to get the selected index value
options[].value - to get the value of the selected item
options[].text - to get the option for the selected item

ex:

var list_box = document.getElementById('id_of_dropdown_box');
list_box.selectedIndex; --> returns the value of selected index(drop down index starts from 0) '1' check

options[0].value --> value of the zero th element '1' check

options[0].text --> text of the zero th element 'Ruby' check

ruby - 'yield' method

2009-11-15T22:10:00.001-08:00

Hi Guys,

Hope most of our ROR developers are using 'yield' method in the layout file. In ruby we are not using the yield method(called from any method). I have come across the 'yield' method, its very interesting to know about the use of that method.

We can use 'yield' method inside any ruby method to execute the code inside the block.

example-1:
class Sample
def check_yield
yield
yield
yield
end
end

in the class 'Sample', i have called the yield method three times inside the method.

obj = Sample.new()
obj.check_yield{puts "hi am in method block"}

Output:
hi am in method block
hi am in method block
hi am in method block

Now i have created an object for the class 'Sample', and called the method 'check_yield' with the block({ }). When i executed the method it prints the results for three times. Because we are calling the yield for three times, the call to yield method executes the code inside the block({puts "hi am in method block"}). That's it.

We can also use the yield method with params.

example-2:
class Sample
def even_nos_upto(param)
for i in 0..param
yield(i) if i%2 == 0
end
end
end

obj = Sample.new()
obj.even_nos_upto(10){|x| puts x}

Output:
0
2
4
6
8
10

In Array, we are using the method 'collect', 'each' to get each value of the array.

[1,2,3,4,5].collect{|x| puts x}

Inside the collect method in Array class, the yield method called to return each value.

class Array
def my_collect
for i in 0..(self.length-1)
value = self[i]
yield(value)
end
end
def collect_greater_than(limit)
for i in 0..(self.length-1)
value = self[i]
yield(value) if value > 5
end
end
end

[1,2,3,4,5,6,7].collect{|x| puts x} # default method collect
[1,2,3,4,5,6,7].my_collect{|x| puts x} # method my_collect
[1,2,3,4,5,6,7].collect_greater_than(5){|x| puts x} # collect with condition

Output:
1
2
3
4
5
6
7
1
2
3
4
5
6
7
6
7

In the above sample, the method 'collect' & 'my_collect' works like a same. And the method collect_greater_than bit different from the first one, it returns the values based on the condition we have used.

has many polymorphic - double sided

2009-10-30T21:03:00.000-07:00

I have used the following model relation to get the has many polymorphic double sided relation.

class Album < ActiveRecord::Base
has_many :album_files, :dependent => :destroy, :foreign_key => "album_id", :class_name => "AlbumFile"
has_many :photos, :source => :file, :through => :album_files, :source_type => "Photo", :class_name => "Photo"
has_many :videos, :source => :file, :through => :album_files, :source_type => "Viedo", :class_name => "Video"
end
class AlbumFile < ActiveRecord::Base
belongs_to :file, :polymorphic => true
end
class Photo < ActiveRecord::Base
has_many :album_files, :dependent => :destroy, :as => :file
has_many :albums, :source => :album, :foreign_key => "album_id", :through => :album_files, :class_name => "Album"
end
class Video < ActiveRecord::Base
has_many :album_files, :dependent => :destroy, :as => :file
has_many :albums, :source => :album, :foreign_key => "album_id", :through => :album_files, :class_name => "Album"
end

thats it..

Now we have associated Album with photos, videos through the mapping table album_files.

Following works for this

album = Album.create()
album.photos << Photo.create()
album.vidoes << Video.create()

album.album_files.count - returns the total count i.e, 2

album.photos - returns the count 1
album.vidoes - returns the count 1