Amit Yadav » Ruby on Rails

Fast-track your Web apps with Ruby on Rails

Amit — Wed, 29 Jun 2011 03:29:23 +0000

Fast-track your Web apps with Ruby on Rails

Ruby on Rails is a recent entry into the world of Web application development that is rapidly gaining mindshare, even while still in beta versions. Rails succeeds by automating the creation of the most common types of Web applications while not straightjacketing you if you want to add custom or atypical requirements. Moreover, compared to many Free Software libraries that perform individual aspects of a Web application, Rails contains a nicely integrated set of tools for all aspects.

Difference between delete and destroy in ActiveRecord

Amit — Wed, 29 Jun 2011 03:26:20 +0000

To delete a particular record we will go for delete or destroy methods.But according to the names both looks very similar, but the functionality wise both are different. so lets check the difference between delete and destroy methods in Active Record.

Now first check what the delete method will do:

Delete method deletes the row with a primary key matching the id argument, using a SQL DELETE statement, and returns the number of rows deleted. Active Record objects are not instantiated, so the object‘s callbacks are not executed, including any :dependent association options or Observer methods.

You can delete multiple rows at once by passing an Array of ids.

It is much faster than the destroy method, skipping callbacks might bypass business logic in your application that makes the function to work fast.

example:
Delete a single row
user.delete(1)

Delete multiple rows
user.delete([2,3,4])

Destroy method:
The destroy method makes the SQL call to the database and destroys the row in the table that contains it. It does still allow you to manipulate the object in the application as long as it’s still in scope (i.e) the callbacks and
filters are allowed even after destroying the object.

example :
Destroy a single object
User.destroy(1)

Destroy multiple objects
users= [1,2,3]
User.destroy(users)

About Rails3 and MVC architecture

Amit — Wed, 29 Jun 2011 03:25:19 +0000

Rails 3:
Rails is a framework to develop web applications in Ruby. And the web application in Rails will be simpler and faster than in other languages. As, rails is an opinionated software, in the development process of an application, rails will do assumptions about our requirements and will generate the required code for the application at various stages, with a little interaction of the developer for few specifications.

Rails has a philosophy includes the following:

1) DRY: (Don't Repeat Yourself)
In rails, it suggests that writing the same code again and again for several times is not a good process. Instead of writing the same code again and again, we can partition that particular part of code in to a seperate block or function or something else and can reuse it whenever and wherever we need it in the current application.

2) Convention over Configuration:
In rails, almost the process of development will be done using the conventions instead of a * configuration settings for our application. If we follow the conventions (guidelines of rails) in development process, everything will be taken care by rails about our application.

3) REST: (Representational State Transfer)
In rails, REST will have two main features. They are:
a) Using resource identifiers like URLs to represent the resources of our application.
b) Transferring the representations of the state of a particular resource among system components.
REST will be useful for routing in our applications for the specification of path for a particular resource. And REST consists of HTTP verbose for our application like:
a) POST b) GET c) PUT d) DELETE.

MVC architecture:
The MVC architecture in Rails application has:

1) Model:
Model will consist of the data about our applications and is used to manipulate the content of models (tables). It will contain the validations, rules and set of guidelines to manipulate our models.

2) View:
View will consist of the templates of html pages, which will be visible for public/user. It will purely concentrate on the representation of data our application.

3) Controller:
Controller is the thing which will have the control over both Model and View. The Controller will receive the requests from the user (from views) and will send that request to respective model to have the information, and will pass the data to the users in form of a view.

The representation of MVC Architecture will be as follows:

View————————–Controller———————–Model
(User interface)————–(Controllers)——————(Databases)

Mutable and Immutable Objects

Amit — Wed, 29 Jun 2011 03:23:43 +0000

Mutable objects :
1)Mutable objects are objects whose state can change.
2)In Ruby, Mutability is a property of an instance.
3)Any instance can become immutable by calling the "freeze".

Immutable objects :
1)Immutable objects are objects whose state never changes after creation.

2)Immutable objects are thread-safe(A piece of code is called as thread-safe ,if it functions correctly during simultaneous execution by multiple threads).

Freezing Objects:
1:The freeze method in class Object prevents you from changing an object, effectively turning an object into a constant.
2:After we freeze an object, an attempt to modify the freezed object, results in TypeError.
3: freeze operates on an object reference, not on a variable.
4:This means that any operation resulting in a new object.

Example:
str = 'A simple string. '
str.freeze
begin
str << 'An attempt to modify.'
rescue => err
puts "#{err.class} #{err}"
end

# The output is – TypeError can't modify frozen string

FFMPEG get video file duration: Ruby

Amit — Tue, 10 Mar 2009 09:51:58 +0000

^?View Code RUBY

def get_video_file_duration(inputFilename)
            command = "ffmpeg -i "
                             + inputFilename.to_s + " 
                             2>&1 | grep 'Duration' 
                             | cut -d ' ' -f 4 | sed s/,//"
                             output = `#{command}`
 
          if output =~ /([\d][\d]):([\d][\d]):([\d][\d]).([\d]+)/
               duration = (($1.to_i * 60 + $2.to_i) * 60 + $3.to_i) * 10 + $4.to_i
          end
 
          #return duration.to_s
          return "#{$2}:#{$3}"
 end

My Google Knol articles

Amit — Mon, 23 Feb 2009 05:17:14 +0000

Ruby on Rails implementation of OpenId

Ruby on Rails implementation for Paypal | Download Code

Ruby on Rails implementation for Authorize.net

How to Create a File Upload Progress Bar in Rails, Passenger, Prototype and Low Pro

Amit — Tue, 17 Feb 2009 07:49:57 +0000

How to Create a File Upload Progress Bar in Rails, Passenger, Prototype and Low Pro from Erik Andrejko on Vimeo.

Rails flash messages helper

Amit — Tue, 17 Feb 2009 07:49:05 +0000

display_flash(:error) # to display a specific flash message
display_flash # to display all flash messages

^?View Code RUBY

# Methods added to this helper will be available to all templates in the application.
module ApplicationHelper
  FLASH_TYPES = [:error, :warning, :success, :message]
  def display_flash(type = nil)
    html = ""
    if type.nil?
      FLASH_TYPES.each { |name| html &lt;&lt; display_flash(name) }
    else
      return flash[type].blank? ? "" : "#{flash[type]}"
    end
    html
  end
end

Beauty of Maths

Amit — Tue, 22 Jul 2008 04:26:38 +0000

1 x 8 + 1 = 9
12 x 8 + 2 = 98
123 x 8 + 3 = 987
1234 x 8 + 4 = 9876
12345 x 8 + 5 = 98765
123456 x 8 + 6 = 987654
1234567 x 8 + 7 = 9876543
12345678 x 8 + 8 = 98765432
123456789 x 8 + 9 = 987654321

1 x 9 + 2 = 11
12 x 9 + 3 = 111
123 x 9 + 4 = 1111
1234 x 9 + 5 = 11111
12345 x 9 + 6 = 111111
123456 x 9 + 7 = 1111111
1234567 x 9 + 8 = 11111111
12345678 x 9 + 9 = 111111111
123456789 x 9 +10= 1111111111

9 x 9 + 7 = 88
98 x 9 + 6 = 888
987 x 9 + 5 = 8888
9876 x 9 + 4 = 88888
98765 x 9 + 3 = 888888
987654 x 9 + 2 = 8888888
9876543 x 9 + 1 = 88888888
98765432 x 9 + 0 = 888888888

Installing mod_rails(Passenger)

Amit — Mon, 14 Jul 2008 04:49:19 +0000

Mod_rails has come to rescue people form tedious rails application development. With mod_rails the work has become a lot easier, you do not have to worry about different things just few steps and your application is up and running, ofcourse there are options to modify the deployment to your needs.

There are few prerequisites for mod_rails to work, first you need Apache and secondly you need Ruby and Rubygems.

Step 1: We need to update rubygems
sudo gem update

Step 2: We need to install mod_rails(passenger)
sudo gem install passenger

Step 3: Now we need to install Apache2 headers
sudo aptitude install apache2-prefork-dev

Step 4: Now we need to install Apache2 module
sudo passenger-install-apache2-module

There will be a screen which takes you further. If there are any dependencies that are needed then it will be asked for on this screen.

After successful installation there is just one thing left, we need to copy some lines to the Apache2 main config file , open the file “apache2.conf” in a text editor and then paste these lines at the end of the file:
LoadModule passenger_module /usr/lib/ruby/gems/1.8/gems/passenger-1.0.4/ext/apache2/mod_passenger.so
RailsSpawnServer /usr/lib/ruby/gems/1.8/gems/passenger-1.0.4/bin/passenger-spawn-server
RailsRuby /usr/bin/ruby1.8

Restart Apache
sudo service apache2 restart

Done!!

Compile & install Nginx web server

Amit — Mon, 23 Jun 2008 05:25:42 +0000

^?View Code RUBY

 # See:
# - http://en.wikipedia.org/wiki/Nginx
# - http://wiki.codemongers.com/NginxGettingStarted
# - http://wiki.codemongers.com/NginxInstallOptions
# - http://wiki.codemongers.com/NginxCommandLine
# - http://wiki.codemongers.com/NginxConfiguration
 
export PATH="/usr/local/bin:/usr/local/sbin:/usr/bin:/bin:/usr/sbin:/sbin"
 
mkdir -p ~/Desktop/Nginx
cd ~/Desktop/Nginx
 
curl -L -O http://sysoev.ru/nginx/nginx-0.7.2.tar.gz
tar -xzf nginx-0.7.2.tar.gz
 
curl -L -O http://downloads.sourceforge.net/pcre/pcre-7.7.tar.gz
tar -xzf pcre-7.7.tar.gz
 
cd ~/Desktop/Nginx/nginx-0.7.2
./configure --help
./configure --prefix=/usr/local/nginx --sbin-path=/usr/local/sbin --with-debug --with-http_ssl_module --with-pcre=../pcre-7.7
make
sudo make install
 
which nginx
otool -L /usr/local/sbin/nginx
open /usr/local/nginx
open -e /usr/local/nginx/conf/nginx.conf
 
nginx -v
nginx -V
sudo nginx # start server
sudo nginx -t
 
open http://localhost:80
open http://localhost:80/50x.html
 
sudo nano /usr/local/nginx/conf/nginx.conf # editing ... server { listen 8080; ...
 
# reload configuration
sudo kill -HUP `cat /usr/local/nginx/logs/nginx.pid`
 
# stop server
sudo kill -15 $(ps -auxxx | egrep "[n]ginx.*master" | awk '{ print $2 }') 2&gt;/dev/null

Create a Hash from two Array objects

Amit — Mon, 23 Jun 2008 04:37:17 +0000

Requires Ruby 1.8.7 or higher.

^?View Code RUBY

keys = [1,2,[3,4]]
[1, 2, [3, 4]]
values = ['a','b',['c','d']]
["a", "b", ["c", "d"]]
Hash[ * keys.zip(values).flatten(1) ]
{1=&gt;"a", [3, 4] =&gt; ["c", "d"], 2 =&gt; "b"}

File Upload Helpers

Amit — Mon, 16 Jun 2008 04:45:02 +0000

Handy little helpers to check if a file was provided to a controller, and to save it.

^?View Code RUBY

 def file_provided?
   [StringIO, Tempfile].include?(@file.class) and @file.size.nonzero?
 end 
 
 def save_file
   if @file.is_a? Tempfile
     FileUtils.cp(@file.path, path)
   elsif @file.is_a? StringIO
     File.open(path, "wb") { |disk_file| disk_file &lt;&lt; @file.read }
   end
 end

Renaming your .rhtml to .erb on EdgeRails

Amit — Mon, 16 Jun 2008 04:43:20 +0000

^?View Code RUBY

## just slap this in your rake file or in lib/tasks
 
namespace 'views' do
  desc 'Renames all your rhtml views to erb'
  task 'rename' do
    Dir.glob('app/views/**/*.rhtml').each do |file|
      puts `svn mv #{file} #{file.gsub(/\.rhtml$/, '.erb')}`
    end
  end
 end
 
 ## or if you have rhtml and rxml you could probably use the following (untested)
 
 namespace 'views' do
   desc 'Renames all your rhtml views to erb'
   task 'rename' do
     Dir.glob('app/views/**/*.rhtml').each do |file|
       puts `svn mv #{file} #{file.gsub(/\.(rhtml|rxml)$/, '.erb')}`
     end
   end
 end

Automatically tagging releases with capistrano

Amit — Mon, 16 Jun 2008 04:36:26 +0000

Even though Capistrano “tags” each release by creating a new folder on the production server(s), it might be interesting to have a historical perspective in your repository anyway. This makes it easier to know exactly what went up for a release. I would like to share the following Capistrano recipe for your pleasure: config/deploy.rb

^?View Code RUBY

 require ‘uri‘
 task :after_deploy do
   source = repository
   dest = URI.parse(repository).merge(“../releases/#{File.basename(release_path)}“)
   cmd = “svn copy –revision=#{revision} –quiet –message \”Auto tagging release #{release_path}\” #{source} #{dest}“
   puts cmd
   `#{cmd}`
 end

First, we start by requiring uri, because Subversion does not like relative URLs. Next, we find the location into which to tag the release, and finally, we just do it. Simple, effective. Enjoy !

Exporting development data to fixture files for your test (Ruby)

Amit — Thu, 12 Jun 2008 05:09:06 +0000

For your unit & functional tests you have to provide input data to your test files and you do that through fixtures. The script below extracts the data from the development data base and puts it to the fixture file for each table.

^?View Code RUBY

namespace :db do
  desc 'Create YAML test fixtures from data in an existing database.
  Defaults to development database. Set RAILS_ENV to override.'
 
  task :extract_fixtures =&gt; :environment do
    sql = "SELECT * FROM %s"
    skip_tables = ["schema_info", "sessions"]
    ActiveRecord::Base.establish_connection
    tables = ENV['FIXTURES'] ? ENV['FIXTURES'].split(/,/) : ActiveRecord::Base.connection.tables - skip_tables
    tables.each do |table_name|
      i = "000"
      File.open("#{RAILS_ROOT}/test/fixtures/#{table_name}.yml", 'w') do |file|
        data = ActiveRecord::Base.connection.select_all(sql % table_name)
        file.write data.inject({}) { |hash, record|
          hash["#{table_name}_#{i.succ!}"] = record
          hash
        }.to_yaml
      end
    end
  end
end

shame.rake

Amit — Thu, 12 Jun 2008 05:03:34 +0000

If you’ve ever been working on a Rails application and found yourself [stupidly] slipping in your testing, We have just the tool for you. Using rake and rubyosa, you can now automatically post your Code to Test Ratio as your iChat status message—meaning you can now use shame and self-humiliation to keep you motivated. After you’ve installed rubyosa, add shame.rake to your lib/tasks directory. The file contains:

^?View Code RUBY

require 'rbosa'
require 'code_statistics'
 
task :shame do
  stats = CodeStatistics.new(*STATS_DIRECTORIES)
  code  = stats.send :calculate_code
  tests = stats.send :calculate_tests
  ichat = OSA.app('ichat')
  msg = "Code To Test Ratio: 1:#{sprintf("%.1f", tests.to_f/code)}"
  ichat.status_message = msg
  $stderr.puts %|iChat status set to: #{msg.inspect}|
end

Simple method to find age of person

Amit — Thu, 12 Jun 2008 04:56:06 +0000

^?View Code RUBY

1
2
3

def age
   ((Time.now - birthday) / (60*60*24)/365.2422).to_i
end

Rails Image Cropping

Amit — Wed, 09 Apr 2008 13:12:53 +0000

I was looking for an UI for image cropping utility for my project and came across this, it was using php as its backend but i changed it to use rails as its backend. The UI is simple and can be incorporated with different backend solutions.

Here is the code.

Rails Cheatsheets

Amit — Fri, 04 Apr 2008 11:48:41 +0000

Here are the rails cheatsheet’s which will help you to get a good overview of how things work in RAILS.

Full Ruby on Rails cheatsheet

Rails File Cheatsheet

Form Helpers

Asserts in Rails

Active Record cheatsheet

rubyonrails-cheatsheet.pdf