https://kinnrot.github.io - Chen Kinnrot - Keep it simple - go to kinnrot.github.io

Watch out for reference duplication instead of instance duplication

2017-07-18T04:42:00.003-07:00

# This code will generate 96 instances

ViewStatData = Struct.new(:total, :target, :ratio)

96.times.map {|_|ViewStatData.new(0, 0, 0)}

# And this will not, it'll generate 96 pointers
[ViewStatData.new(0, 0, 0)] * 96
# So Watch out!!!

Ruby Lazy chunked hash like behavior

2017-06-05T05:11:00.001-07:00

When we want to iterate a long list, we can simply write a query and get a cursor, ActiveRecord will do all the heavy lifting for us.

What happens when we need to do some complicated computations on a set of data, which sometimes can be too big to be stored in memory for the entire computing process?

This is when we need to start being more creational.

I'd like to introduce what I came up with.

The problem:

- Complex calculation on time based data series for a period of 3 months.
- Each calculation may depends on previous one and on future and past data.
- Must be in order.
- When fetching all data server crash on memory.

The solution:

I wanted to do the most minor code change possible, and currently the data was accessed via a hash.
I decided to encapsulate the hash with something I called lazy chunked hash (tried google it see it as standard behavior in clojure).

It looks like this:

class ValuesProvider  def initialize()
    @loaded_date = nil

    @hash = Hash.new(0)
  end
  def [](time_slot)
    get(time_slot)
  end
  private
  def get(time_slot)
    relevant_date = time_slot.to_date
    unless relevant_date == @loaded_date      load(relevant_date)
    end
    @hash[time_slot.to_i]
  end

end

Pretty simple and does the work, instead of loading the data all at once, the data is being loaded for each day separately, this way we keep it chunky but not too chunky.

And best part, my code that consume the data, didn't change because of the [] method, which makes my ValueProvider behave like an array.

This solution is good when the consumer data request(call for[]) implies on what data should be loaded, which most of the times will, but in some cases it won't)

Rubymine on OSX memory issues

2015-01-06T13:32:00.001-08:00

I found this only today, you should run Rubymine as 32 bit process.
It works much faster and consume half the memory.

To set this got to the Applicaitons folder right click on rubymine->get info and check the "open in 32 bit mode"

Thats all!

Use FactoryGirl And Faker for easy data generation in unit testing (Part1)

2014-11-15T07:52:00.001-08:00

The most irritating thing in writing tests is the data generation preparation process, sometimes you want to create an object with 20 fields that 10 of them are mandatory but you only care about the value of 1, and you don't want to mock, cause you interact with other methods and object that fetch this model from db.

To me it happens a lot so I found the FactoryGirl + Faker combination that made my life much more easy and now I can write tests in peace.

To add them just put in Gemfile:

gem "factory_girl_rails", "~> 4.0"
gem "faker"

So lets take a complex sample to explain all there is to know.

We have a User, the User belongs to a Company, User has many tasks.

Company has many irritating mandatory fields

Lets define the Company Factory:

FactoryGirl.define do
    factory :company do
      name {Faker::Name.name}
      trp {Faker::Number.between(0,10)}
      grp {Faker::Number.between(0,5)}
      budget {Faker::Number.number(4)}
      cpm {Faker::Number.between(1,70)}
      trp_price {Faker::Number.between(100,700)}
      viewer {Faker::Number.between(0,100000)}
      total_viewer {Faker::Number.between(0,200000)}
      unique_viewer {Faker::Number.between(0,50000)}
      spots {Faker::Number.between(0,1000)}
    end
  end

As you can see I define lots of fields with random values.

Now we can create a company by writing

create(:company)

Or just build one (without save to db) by calling

build(:company)

That's all for now, I'll continue in part2.

Get the user locale from http headers

2014-11-15T07:42:00.001-08:00

If you want to provide default localization support for guest user in your website yo can locate their browser locale by the following code:

def extract_locale_from_header
    unless request.env['HTTP_ACCEPT_LANGUAGE'].nil?
      return request.env['HTTP_ACCEPT_LANGUAGE'].scan(/^[a-z]{2}/).first
    end
    'en'
  end

This way you can determine on server side the locale of the user currently entered your site.

Dedicating a DJ(Delayed job) worker to a specific queue in heroku.

2014-11-15T07:34:00.002-08:00

Let's say you have a vey important procedure that takes a while, and you need to process it in background, but you still want to execute ASAP.

I'm using Delayed Job on Heroku, and could not find a lot of tutorials to do this simple task.

So here is the simplest way to achieve this ability, you can raise a process/deamon that will have only one queue to work on. (Dealyed job worker by default is queue agnostic, just process all jobs)

In procfile:

urgentworker: QUEUE=urgent bundle exec rake jobs:work

You can call the worker in any name you want and even define multiple workers for multiple queues.
And in the "urgent" job just define the queue name to be "urgent" the worker will process only jobs in this queue.

example:

handle_asynchronously :some_job, :queue => "urgent'

This will also work for Resque.

Notice that for rescue you can write QUEUE=* but for delayed job you can't.

Overriding default id in mongoid

2014-11-15T07:20:00.000-08:00

This is an easy one, just want to make sure it's clear.

Add the following field to your model:

field :_id, type: Moped::BSON::ObjectId

And to allow setting it:

1 def id=(id)
2   self[:_id] = id
3 end

Now you can just do obj.id=[Some ObjectId] and save the object.

Nice post about cyber war

2014-10-05T00:42:00.001-07:00

Popular Science: The War Of Zeros And Ones. http://google.com/newsstand/s/CBIwvZm5zho

ClusteTV is hiring

2014-08-08T07:40:00.000-07:00

Cluster TV is looking for it's next programmer/Superstar!

If you can:

* Write code like an Effin' machine

* Test your OWN code

* Speak English like it's your mother's tongue

* Handle challenges

* Be self-driven & independent

We would also appreciate if you'll have:

* Great communications skills

* Independent thinking

* Passion to learn new things

* RoR or Angular experience

* Coffee script knowledge

* NOSQL understanding

Then we want you!

What we offer:

* Great and professional team.

* Opportunity to become an integral part of an innovative TV solution.

* A chance to learn from the best in the industry.

* Full time job in the Tel Aviv area.

* Unlimited supply of food and beer. Really.

* Flexible work hours.

If you like what you see and have da skillz, drop us an email at chen@clustertv.com
Or, call me tel: +972 542124335.

Good luck!

Karma Rails Angular Jasmine testing - set up in 5 minutes

2014-02-02T23:32:00.001-08:00

It took me about an hours and a half because google is not up to date, so here it is:

First - as a rails developer, if you don't have node.js, this is the time to install it.
If you don't use RubyMine as you IDE, I recommend it as well, but whatever you prefer is fine by me.
Here you'll fins instructions about karma installation, follow them carefully.

You'll see that you need to tell karma where is your sources and test sources.

I'm working with jasmine, and using angular as a gem, check my configuration:

frameworks: ['jasmine'],

// list of files / patterns to load in the browser
files: [
//libs

'http://0.0.0.0:3000/assets/application.js',
'/Users/chen/.rvm/gems/ruby-1.9.3-p448/gems/angularjs-rails-1.2.9/vendor/assets/javascripts/angular-mocks.js',
'spec/javascripts/controllers/sample.js',

'spec/javascripts/controllers/*/*_spec.js.coffee',
'spec/javascripts/controllers/**/*_spec.js.coffee',
'spec/javascripts/controllers/**/*_spec.coffee',
'spec/javascripts/controllers/**/*_spec.js'
]

To things you should notice:
1. I use rails assets pipeline to give all my app code js, (just run your server before you test)
2. I add the angular mocks lib

All other stuff are basic, I got code in coffee and js so needed a little more lines to find all my tests.

this is the way to make this work pretty fast.

Export Hebrew (or any non english language) with php to excel

2014-01-12T14:09:00.002-08:00

I found it very annoying that php data to excel is not so straight forward as one might think ,lots of wrong stuff here.

The thing is, as a developer you don't know a lot about encoding.

So you don't really think about it until you have bugs, than you start searching for a better solution, I found this.

Meaning you manually convert encoding to support excel, and add BOM.

Just wanted to gather a few links together for future use.

Enjoy.

Home Base SDK

2013-01-28T06:10:00.001-08:00

As a developer@widdit's incredible android team, I decided to write a how to embed Widdit's home base sdk in 5 minutes guide, so here it is:

Step 1:
go to widdit.com and create an account.

Step 2:
create your first home base in the home base section at widdit site.

step 3:
go to sdk's tab and follow the installation instructions

step 4:
upload your new apk to the market

step 5:
make money!

Good luck.

SpineJS Tip

2012-12-05T06:02:00.003-08:00

Never create multiple instances of a controller that generates the same view, cause you're event's registrations will be duplicated over and over again!

Avoid usage of AsyncTask Class on android

2012-09-26T09:40:00.001-07:00

Just noticed this method available from API 11 only, so you should find another implementation to avoid unexpected behaviour.

Or don't call the execute method, why? If you'll check documentation you'll see that in some versions of android all tasks will run synchronouslly on the same background thread and on some versions it'll run on a pool of threads. Always use the executeOnExecutor option for consistent behaviour between platform version and avoid unexpected behaviour.

See docs

Nice idea for what's new in my app

2012-08-31T01:05:00.001-07:00

People probably don't read/understand what's new in an app when they update it. Skype did a very nice screen that shows you that something did change

coffee-script is another piece of shit

2012-07-08T15:18:00.004-07:00

Hi,

A few months ago I discovered this new stuff called coffee script, and thought to myself, "this is awesome I'll write less and do more" Today, I tried to continue a development of a pretty fat client side and tried to find myself in the 1000 lines of code I wrote so far (not so many). It was pretty hard, and I'm the only programmer for now, can't imagine how a new programmer would enter to this project.

So...
coffee-script is java-script that look better, no other benefits, and if you plan to write a little more than 200 lines of code, consider using some strongly typed language(that can generate debugable java script) with good IDE that'll help you maintain your code.

php post response script execution

2012-07-07T09:27:00.003-07:00

I guess it's nice to have so here you go

/*
 * basically allow a php script to return a response and continue with
 * code execution, good for statistics.
 * before echo anything to user call begin and after call end, than you can continue doing stuff
 */
class ScriptContinuationManager
{
    /**
     * this is the point where we need to give a sign to this class
     * that we wanna write our response.
     * @return void
     */
    public function beginRespone()
    {
        ob_end_clean();
        header("Connection: close");
        ignore_user_abort(); // optional
        ob_start();

    }

    /*
     * after this function execution the response will be sent to the
     * client, and code continue without client need to wait.
     */
    public function endResponse()
    {
        $size = ob_get_length();
        header("Content-Length: $size");
        ob_end_flush(); // Strange behaviour, will not work
        flush(); // Unless both are called !

    }
}

2012-06-12T04:57:00.003-07:00

For all you android developers, If you ever installed a new rom and didn't see any logs from your cat, just do this:

http://stackoverflow.com/a/7272831/67505

Rails + Mongo + Heroku how?

2012-03-28T17:12:00.001-07:00

After a few hours of fighting with google I decided to write it all here:

*This post is more relevant for windows users but can help others.

What do you need to have:
First you need to have ruby 1.9.2+
Devkit
then you need rails 3+
then u need the bundler gem
then go to getting started with mongoid
then install mongo locally
then check it all good
then add acoount in heroku
then create app
then add your key
then push

CoffeeScript - language review

2012-02-18T06:30:00.000-08:00

This weekend I learned a new programming language, called coffee script, It's not a real language it's actually compiled to JavaScript, so it's a way to write JavaScript differently.

After a little hands-on and one book read I can say that this is a good language for experienced and non experienced JavaScript programmers.

What's awesome about this language is that is fills like someone took all the good stuff from ruby python and java, and put it in one language that eliminates all the crap you need to take form JavaScript programming.

I can start writing all the good stuff about coffee but there is no need just dive into

http://coffeescript.org/ and you'll understand all the benefits.

PHP Sessions

2012-01-07T14:42:00.000-08:00

One more thing,

If you do stuff like put instances of classes inside a session and expect to call methods of this classes later, you must put the session start after you include the classes definitions.

But I suggest not to do this kind of stuff.

PHP sessions - stuff to check when things goes wrong.

2012-01-06T01:49:00.000-08:00

There is too much information about problems with sessions in PHP, every dude got it's own problem and it's own solution.
The probability that the problem you experiencing is the same is very low.
So here is what my little (and very annoying) google journey came up to:

You must call session_start(); on each page
If you use the header('Location: blabla'); you should use relative url to keep preserve session
some people say before using the header action you need to call session_write_close(); - I'm not using it.
session_write_close(); could be the reason to your problems, cause after calling it you can't modify the session (in the current http context), that was my problem.
on php docs, they say that "Session ID is not passed with Location header even if session.use_trans_sid is enabled. It must by passed manually using SID constant."

So first make sure you use session start, if you passed this search for voodoos like session_write_close() in the middle of your infrastructure and remove them.

If I didn't help, continue the journey.

End of job check list

2011-11-16T00:30:00.000-08:00

I'm about to end my first gig(already end! yay I'm free!) as a programmer, and want to leave a clean desk. So here is a list of things I'm doing and suggest you all do before you move to your next gig:

1. Write about your major infrastructure developments on your wiki or any other system you got, in an easy to understand language.
2. Start lecturing your co-workers about complex parts you developed.
3. Make sure you got full code coverage with unit tests.
4. Search for to-do comments and make sure you do those todo's.
5. If you got unfinished work and think it's worth something make sure someone complete.

And the most important: change your phone number :-) (Bazinga).

Startups: reshare very nice research

2011-10-28T02:00:00.001-07:00

The Startup Gamble [infographic] | Daily Infographic

Rubymine recommended font for windows

2011-09-27T06:43:00.000-07:00

Didn't find a lot about it on internet so:

File->Settings->Editor->colors & fonts->Font
first save as current schema
than click the ... button choose Consolas and set size to 14

looks much better!