Fun On Rails

Grape API authentication using Devise Auth Token

Thu, 27 Mar 2014 02:18:53 +0530

In previous post we saw how to buil RESTful API using Grape. In this post we will see how to add devise auth token to users and how to use it in Grape API authentication.

Lets see how this can be done assuming you already have devise setup ready.
## Add token_authenticable to devise modules (works with devise versions <=3.2)
In user.rb add :token_authenticatable to the list of devise modules, it should look something like below:

## Generate Authentication token on your own (If devise version > 3.2)

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>class User < ActiveRecord::Base </div></div><div data-line='2' class='code-highlight-row numbered'><div class='code-highlight-line'># ..code.. </div></div><div data-line='3' class='code-highlight-row numbered'><div class='code-highlight-line'> devise :database_authenticatable, </div></div><div data-line='4' class='code-highlight-row numbered'><div class='code-highlight-line'> :invitable, </div></div><div data-line='5' class='code-highlight-row numbered'><div class='code-highlight-line'> :registerable, </div></div><div data-line='6' class='code-highlight-row numbered'><div class='code-highlight-line'> :recoverable, </div></div><div data-line='7' class='code-highlight-row numbered'><div class='code-highlight-line'> :rememberable, </div></div><div data-line='8' class='code-highlight-row numbered'><div class='code-highlight-line'> :trackable, </div></div><div data-line='9' class='code-highlight-row numbered'><div class='code-highlight-line'> :validatable </div></div><div data-line='10' class='code-highlight-row numbered'><div class='code-highlight-line'> </div></div><div data-line='11' class='code-highlight-row numbered'><div class='code-highlight-line'> attr_accessible :name, :email, :authentication_token </div></div><div data-line='12' class='code-highlight-row numbered'><div class='code-highlight-line'> </div></div><div data-line='13' class='code-highlight-row numbered'><div class='code-highlight-line'> before_save :ensure_authentication_token </div></div><div data-line='14' class='code-highlight-row numbered'><div class='code-highlight-line'> </div></div><div data-line='15' class='code-highlight-row numbered'><div class='code-highlight-line'> def ensure_authentication_token </div></div><div data-line='16' class='code-highlight-row numbered'><div class='code-highlight-line'> self.authentication_token ||= generate_authentication_token </div></div><div data-line='17' class='code-highlight-row numbered'><div class='code-highlight-line'> end </div></div><div data-line='18' class='code-highlight-row numbered'><div class='code-highlight-line'> </div></div><div data-line='19' class='code-highlight-row numbered'><div class='code-highlight-line'> private </div></div><div data-line='20' class='code-highlight-row numbered'><div class='code-highlight-line'> </div></div><div data-line='21' class='code-highlight-row numbered'><div class='code-highlight-line'> def generate_authentication_token </div></div><div data-line='22' class='code-highlight-row numbered'><div class='code-highlight-line'> loop do </div></div><div data-line='23' class='code-highlight-row numbered'><div class='code-highlight-line'> token = Devise.friendly_token </div></div><div data-line='24' class='code-highlight-row numbered'><div class='code-highlight-line'> break token unless User.where(authentication_token: token).first </div></div><div data-line='25' class='code-highlight-row numbered'><div class='code-highlight-line'> end </div></div><div data-line='26' class='code-highlight-row numbered'><div class='code-highlight-line'> end</div></div></pre></div>

Add migration for authentiction token

rails g migration add_auth_token_to_users
      invoke  active_record
      create    db/migrate/20140326204628_add_auth_token_to_users.rb

Edit migration file to add :authentication_token column to users

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'># db/migrate/20140326204628_add_auth_token_to_users.rb </div></div><div data-line='2' class='code-highlight-row numbered'><div class='code-highlight-line'>class AddAuthTokenToUsers < ActiveRecord::Migration </div></div><div data-line='3' class='code-highlight-row numbered'><div class='code-highlight-line'> def self.up </div></div><div data-line='4' class='code-highlight-row numbered'><div class='code-highlight-line'> change_table :users do |t| </div></div><div data-line='5' class='code-highlight-row numbered'><div class='code-highlight-line'> t.string :authentication_token </div></div><div data-line='6' class='code-highlight-row numbered'><div class='code-highlight-line'> end </div></div><div data-line='7' class='code-highlight-row numbered'><div class='code-highlight-line'> </div></div><div data-line='8' class='code-highlight-row numbered'><div class='code-highlight-line'> add_index :users, :authentication_token, :unique => true </div></div><div data-line='9' class='code-highlight-row numbered'><div class='code-highlight-line'> end </div></div><div data-line='10' class='code-highlight-row numbered'><div class='code-highlight-line'> </div></div><div data-line='11' class='code-highlight-row numbered'><div class='code-highlight-line'> def self.down </div></div><div data-line='12' class='code-highlight-row numbered'><div class='code-highlight-line'> remove_column :users, :authentication_token </div></div><div data-line='13' class='code-highlight-row numbered'><div class='code-highlight-line'> end </div></div><div data-line='14' class='code-highlight-row numbered'><div class='code-highlight-line'>end</div></div></pre></div>

Run migrations

rake db:migrate

Generate token for existing users

We need to call save on every instance of user that will ensure authentication token is present for each user.

Secure Grape API using auth token

You need to add below code to the API::Root in-order to add token based authentication. If you are unware of API::Root then please read Building RESTful API using Grape

In below example, We are authenticating user based on two scenarios
- If user is logged on to the web app then use the same session
- If session is not available and auth token is passed then find user based on the token

<div class='code-highlight'><pre class='code-highlight-pre'><div </div></div><div data-line='2' class='code-highlight-row numbered'><div class='code-highlight-line'># lib/api/root.rb class="k">module API class Root < Grape::API prefix 'api' format :json </div></div><div data-line='7' class='code-highlight-row numbered'><div class='code-highlight-line'> rescue_from :all, :backtrace => true error_formatter :json, API::ErrorFormatter </div></div><div data-line='10' class='code-highlight-row numbered'><div class='code-highlight-line'> before do error!("401 Unauthorized", 401) unless authenticated end </div></div><div data-line='14' class='code-highlight-row numbered'><div class='code-highlight-line'> helpers do def warden env['warden'] end </div></div><div data-line='19' class='code-highlight-row numbered'><div class='code-highlight-line'> def authenticated return true if warden.authenticated? params[:access_token] && @user = User.find_by_authentication_token(params[:access_token]) end </div></div><div data-line='24' class='code-highlight-row numbered'><div class='code-highlight-line'> def current_user warden.user || @user end end </div></div><div data-line='29' class='code-highlight-row numbered'><div class='code-highlight-line'> mount API::V1::Root mount API::V2::Root end class="k">end</div></div></pre></div>

Building RESTful API using Grape in Rails

Wed, 26 Mar 2014 12:39:27 +0530

While developing a rich client side web application or mobile app, we need RESTful JSON API which interacts with the front-end javascript framework. Here you may use backbone.js, ember.js or angular.js on the front-end side of application.

Here we’ll be using Ruby on Rails on the back-end which will serve JSON API consumable by fron-end framework. If you look at the ruby toolbox you’ll see many API Builder gems available but it seems grape can be a good choice.

Grape is a RESTful API microframework built to easily and quickly produce APIs for Ruby-rooted web applications.

Let’s see how we can build RESTful JSON apis using Grape library:

Getting Started

Add grape to your Gemfile and then run bundle install

gem 'grape'

Modularizing API directory structure

Place API files into lib/api. You need to create api folder inside lib directory.
As we are placing api directory inside lib you don’t need to explicitly load it inside application.rb
If you want to place api directory at some other place then add below lines to to application.rb

config.paths.add "app/api", glob: "**/*.rb"
config.autoload_paths += Dir["#{Rails.root}/app/api/*"]

First, Let’s create API::Root class that will mount available api versions.

# lib/api/root.rb
module API
  class Root < Grape::API
    prefix 'api'
    mount API::V1::Root
    # mount API::V2::Root (next version)
  end
end

Now, create a API::V1::Root class that will mount resources for version 1

# lib/api/v1/root.rb
module API
  module V1
    class Root < Grape::API
      mount API::V1::Posts
      mount API::V1::Authors
    end
  end
end

Now, add resource Posts available for api access in json format

# lib/api/v1/posts.rb
module API
  module V1
    class Posts < Grape::API
      version 'v1'
      format :json
 
      resource :posts do
        desc "Return list of recent posts"
        get do
          Post.recent.all
        end
      end
    end
  end
end

Now, lets add one more resource Authors to version v1

# lib/api/v1/authors.rb
module API
  module V1
    class Authors < Grape::API
      version 'v1' 
      format :json 
 
      resource :authors do
        desc "Return list of authors"
        get do
          Author.all
        end
      end
    end
  end
end

Mounting API under rails routes

Mount API::Root under routes pointing to rails root

# config/routes.rb
SampleApp::Application.routes.draw do
  mount API::Root => '/'
end

Customize JSON API Errors

We can control the api raised errors and customize them so that response is in our own format whenever there are exceptions.

# lib/api/error_formatter.rb
module API
  module ErrorFormatter
    def self.call message, backtrace, options, env
      { :response_type => 'error', :response => message }.to_json
    end
  end
end

Now, you can plug this module inside API::Root

# lib/api/root.rb
module API
  class Root < Grape::API
    #...
    error_formatter :json, API::ErrorFormatter
    #...
  end
end

You can override error formatter for particular api version. Let’s customize errors for API::v1::Root:

#lib/api/v1/error_formatter.rb
module API
  module V1
    module ErrorFormatter
      def self.call message, backtrace, options, env
        { :response_type => 'error', :response => message }.to_json
      end
    end
  end
end
 
# lib/api/v1/root.rb
module API
  module V1
    class Root < Grape::API
      #...
      error_formatter :json, API::V1::ErrorFormatter
      #...
    end
  end
end

Accessing API routes

If you do rake routes | grep api then it will list only mount path for api but do not list all the paths.

rake routes | grep api
    api_root        /api                API::Root

So, in-order to list all api paths, you may have to create api routes task:

# lib/tasks/routes.rake
namespace :api do
  desc "API Routes"
  task :routes => :environment do
    API::Root.routes.each do |api|
      method = api.route_method.ljust(10)
      path = api.route_path.gsub(":version", api.route_version)
      puts "     #{method} #{path}"
    end
  end
end

Now, run task and it should print routes like this:

rake api:routes
    GET        /api/v1/posts(.:format)
    GET        /api/v1/authors(.:format)

Securing API

Now we have got Grape API ready and working properly. Lets see how we can secure API. There are many approaches to authenticate API. Here lets first get it working with simple HTTP Basic authentication.

HTTP Basic authentication

In our case, lets add basic authentication to the API::Root and it will get applied to all versions of API.

# lib/api/root.rb
module API
  class Root < Grape::API
    #...
 
    http_basic do |email, password|
      user = User.find_by_email(email)
      user && user.valid_password?(password)
    end
    #...
  end
end

Requesting API using basic http auth credentials:

curl http://localhost:3000/api/products -u "admin:secret"

Authenticate using email and password

Grape provides us with before block inside that we can add authenctication code.

# lib/api/root.rb
module API
  class Root < Grape::API
    #...
    before do
      error!("401 Unauthorized", 401) unless authenticated
    end
 
    helpers do
      def authenticated
        user = User.find_by_email(params[:email])
        user && user.valid_password?(params[:password])
      end
    end
    #...
  end
end

Understanding RESTful vs SOAP web services

Mon, 17 Mar 2014 15:09:33 +0530

A Web service is a method of communications between two electronic devices over the World Wide Web.
It is also defined as a software system designed to support interoperable machine-to-machine interaction over a network.

In simple words, “Web services are developed to use by other software applications”

Web services communicate via either SOAP or REST messages.

REST

REST stands for REpresentational State Transfer. It is a term coined by Roy Fielding in his Ph.D. dissertation
It is an architecture style for designing networked applications which typycally runs runs over HTTP.

REST is an architecture and not a “standard”. There is no w3c recommendation for REST. It is concept for better web and widely accepted.

RESTful applications use HTTP requests to post data (create and/or update), read data (e.g., make queries), and delete data. Thus, REST uses HTTP for all four CRUD (Create/Read/Update/Delete) operations.

It expects client to have knowlege of what to send and what to expect in response. It is focused on accessing named resources through a single consistent interface.

Highlights:

It is simple
It is lightweight and faster
Platform-independent
Language-independent
runs over HTTP
Response can be returned in “XML/JSON” format

Like Web Services, REST offers no built-in security features, encryption, session management, QoS guarantees, etc. But also as with Web Services, these can be added by building on top of HTTP:

For security, username/password tokens are often used.
For encryption, REST can be used on top of HTTPS (secure sockets).

Example:

The Web is comprised of resources. A resource is any item of interest. For example, A software company may have many products. Clients may access particular product with this URL:

http://www.<company>.com/products/7

SOAP

SOAP, originally defined as Simple Object Access Protocol. It is a protocol specification for exchanging structured information in the implementation of Web Services in computer networks.

SOAP is an XML based protocol for accessing Web Services.
It is designed to handle distributed computing environments.

It is well defined mechanism for describing the interface e.g. WSDL+XSD, WS-Policy. As it is standardised it becomes complex t
It provides a large number of supporting standards for security, reliability, transactions.

Here content of the message decides what to perform and reponse (payload) must comply with SOAP schema.

Example

It defines 3 fundamental properties:

What service does: Operations provides
How service is accessed: Data format and protocol details
Where a service is located: Adress (URL) details

Sample SOAP request structure:

In the example below, a GetStockPrice request is sent to a server. The request has a StockName parameter, and a Price parameter that will be returned in the response. The namespace for the function is defined in “http://www.example.org/stock”.

POST /InStock HTTP/1.1
Host: www.example.org
Content-Type: application/soap+xml; charset=utf-8
Content-Length: 299
SOAPAction: "http://www.w3.org/2003/05/soap-envelope"
<!- ->
<?xml version="1.0"?>
<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope">
  <soap:Header>
  </soap:Header>
  <soap:Body>
    <m:GetStockPrice xmlns:m="http://www.example.org/stock">
      <m:StockName>IBM</m:StockName>
    </m:GetStockPrice>
  </soap:Body>
</soap:Envelope>

Sample SOAP response structure:

HTTP/1.1 200 OK
Content-Type: application/soap+xml; charset=utf-8
Content-Length: nnn
 
<?xml version="1.0"?>
<soap:Envelope
xmlns:soap="http://www.w3.org/2001/12/soap-envelope"
soap:encodingStyle="http://www.w3.org/2001/12/soap-encoding">
 
<soap:Body xmlns:m="http://www.example.org/stock">
  <m:GetStockPriceResponse>
    <m:Price>34.5</m:Price>
  </m:GetStockPriceResponse>
</soap:Body>
 
</soap:Envelope>

Highlights

Here are few reasons for which you may want to use SOAP:

Platform and laguage independent
Follows W3C standard
WSDL (Web services description language) is a W3C standard based on xml and is used to describe web services.
Security
It supports SSL (just like REST). It also provides a standard implementation of data integrity and data privacy. Being “Enterprise” it’s more secure.
Atomic Transactions
It supports ACID Transactions (WS- Atomic Transactions) so it can provide two phase commit over distributed transactional resources.
Reliable Messaging
It has successful/retry logic built in and provides end-to-end reliability even through SOAP intermediaries

Whenever complex or likely to change API getting developed then SOAP could be a good choice.

References used

http://rest.elkstein.org/
http://www.xfront.com/REST-Web-Services.html
http://www.ics.uci.edu/~fielding/pubs/dissertation/top.htm
http://www.w3schools.com/webservices/ws_soap_example.asp
http://www.slideshare.net/kverbert/soapbased-web-services

Migrating from blogspot to octopress

Sun, 09 Feb 2014 19:00:56 +0530

I was happily writing my blog at blogspot almost three plus years. From last 2-3 days, i was evaluating with octopress for its way of writing posts, customizations, themes, and plugins. As a result of evaluation, found octopress blog as very quick & easy to write hence decided to shift from blogger to octopress.

Below post explains steps involved in migration:

Export content from blogger

First, you need to export your posts from blogger.
Goto blogger admin area and then go to settings >> other >> Export Blog and click on it. Please wait sometime and popup will comeup allowing you to download blog in xml format.

If you still finding some problem with exporting then see here

Formatting posts for octopress

Now the big challenge ! We have xml posts downloaded from blogger but octopress posts format is different.
So, we need to convert xml posts to markdown formatted octopress posts.
If you do it manually then its not an easy task but don’t worry. There is already a ruby code that will do it for you.
Thanks to Reinaldo de Souza for sharing the script. Download the import.rb script from here

Run the script against downloaded xml file

Script requires nokogiri. if you not don’t have already then install using gem install nokogiri
After successful run, this will be creating static markdown octopress formatted posts inside _posts and _drafts directories.

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>ruby import.rb blog-02-09-2014.xml</div></div></pre></div>

Copy generated posts to octopress blog posts

mv _posts/* blog/_posts/`
mv _drafts/* blog/_drafts/`

This finishes migration and run rake preview and you will start seeing your blogger posts.

Writing Octopress blog posts using markdown

Fri, 07 Feb 2014 19:20:07 +0530

This is an example post which shows various markdown syntax that can be used while writing octopress markdown posts.
## Bold text
Hello Octopress!

Blockquote

Don’t stop when you’re tired, stop when you’re done.

@TheJeetBanerjee

We have to go for what we think we’re fully capable of, not limit ourselves by what we’ve been in the past.

@Vivek Paul

Ruby

class A
  def abc
    puts 'hii'
  end
end

Console

$ sudo apt-get install cakePHP

$ git clone git@github.com:imathis/octopress.git # fork octopress

Coffeescript

$('.help').html "(?)"
console.log "print something"
# sum function
sum = (a, b) ->
  a + b

Gist Embedding

multiple-ssh-configlink

# Default GitHub user (sandip)
Host github.com
  HostName github.com
  User git
  IdentityFile /home/sandip/.ssh/id_rsa
 
# github user (client)
Host github-client
  HostName github.com
  User git
  IdentityFile /home/sandip/.ssh/id_rsa_client
 
# github user (friend)
Host github-swapnil
  HostName github.com
  User git
  IdentityFile /home/sandip/.ssh/id_dsa_swapnil

Include Code Snippets

{% include_code path/to/file [title] [lang:language] [start:#] [end:#] [range:#-#] [mark:#,#-#] [linenos:false] %}

Selecting tags from sentence

This is a ruby and rails blog

Pullquote

## Images

AngularJS Tutorial - YouTube

AngularJS is a client-side JavaScript framework.A video tutorial to help you get started with AngularJS.

Inline HTML

<div class='well'>
  All is well. Way to go !!
</div>

Getting started: Octopress powered and Github hosted blog

Fri, 07 Feb 2014 19:20:07 +0530

There are various blogging sites like blogspot, wordpress, posterous, and many more.
Each has their own pros and cons and none of the engine gives us full power of ehhance our blogging experience.
Anyone who has atleast some technical knowledge can start with octopress powered blog. This gives us the power of freedom of doing anything.
So, Lets first understand about octopress framework and its features.

Octopress

Octopress is a framework designed by Brandon Mathis for Jekyll, the blog aware static site generator. If you wanted to know more then it can be found here

Octopress Setup

1. Before starting make sure you have git installed.
If not then do install using,

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>sudo apt-get install git</div></div></pre></div>

2. Install ruby 1.9.3 or higher
Make git clone of octopress source code

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>git clone git://github.com/imathis/octopress.git octopress </div></div><div data-line='2' class='code-highlight-row numbered'><div class='code-highlight-line'>cd octopress </div></div><div data-line='3' class='code-highlight-row numbered'><div class='code-highlight-line'>bundle install</div></div></pre></div>

Installing Octopress theme

Install the default Octopress theme using

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>rake install</div></div></pre></div>

In order to install custom themes,
Please browse through themes and make a selection for your blog.
Once choice is made, you need to do git clone of theme source and install it.

cd octopress
git clone https://github.com/kAworu/octostrap3 .themes/octostrap3
rake 'install[octostrap3]'

To genrate infrastrcture for your blog i.e. layouts, js and css

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>rake generate</div></div></pre></div>

Edit _config.yml to configure blog title, header, metadata, plugins and 3rd Party Settings.
more on configurations can be found here.

We are almost done, and now ready to create our first blog post -

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>rake new_post[“My first octopress post”] </div></div><div data-line='2' class='code-highlight-row numbered'><div class='code-highlight-line'>mkdir -p source/_posts </div></div><div data-line='3' class='code-highlight-row numbered'><div class='code-highlight-line'>Creating new post: source/_posts/2014-02-09-my-first-octopress-post.markdown</div></div></pre></div>

Now you can open a post inside editor and change as you wanted. More on writing markdown can be found here and here too

Well ! Now its time to see, how our blog looks like -

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>cd octopress </div></div><div data-line='2' class='code-highlight-row numbered'><div class='code-highlight-line'>rake watch </div></div><div data-line='3' class='code-highlight-row numbered'><div class='code-highlight-line'>rake preview</div></div></pre></div>

Visit browser http://localhost:4000 and you should be seeing blog running there :-)

Deployment

There are ways to deploy octopress blog. You can either deploy this blog on heroku or on github using github pages.

1. Heroku:
As heroku provides free hosting (1 node) you may want to deploy at heroku.
More on this deployment can be found here

2. With Github Project Pages:
Github provides free static website hosting using github pages and deployment is also very simple.

Note: You should have a github repository called username.github.io

cd octopress
rake setup_github_pages
git remote add origin git@github.com:username/username.github.io.git
rake generate
rake deploy

Visit http://username.github.io to see your blog hosted on github.
Also, do not forget to commit and push your source code on github.

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>git add . </div></div><div data-line='2' class='code-highlight-row numbered'><div class='code-highlight-line'>git commit -m ‘octopress first blog’ </div></div><div data-line='3' class='code-highlight-row numbered'><div class='code-highlight-line'>git push origin source</div></div></pre></div>

Adding custom domain

First create a CNAME file and add naked domain name to it.

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>echo ‘funonrails.com’ » source/CNAME</div></div></pre></div>

Then goto your domain provider website and point your domain i.e A record to github ip address 204.232.175.78.
## Adding subdomain
If you want to point subdomain to github blog then -

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>echo ‘blog.sandipransing.in’ » source/CNAME</div></div></pre></div>

then go to your domain provider website and create a CNAME record for your subdomain i.e. blog pointing to yourname.github.io.
If you want more help on this then please see here and also here

what is new in rails 3

Sun, 17 Mar 2013 14:33:56 +0530

Rails 3 has released with various notable features and said that it’s one of the best version rails community has released so far.

Highlights of major features:

1. Brand new router with an emphasis on RESTful declarations

2. New Action Mailer API modeled after Action Controller

3. New Active Record chainable query language built on top of relational algebra

4. Unobtrusive JavaScript helpers with drivers for Prototype, jQuery, and more coming (end of inline JS)

5. Explicit dependency management with Bundler

Dynamic conditions to rails associations

Thu, 25 Oct 2012 16:12:00 +0530

We all know that rails models associations gets defined while class definitions are loaded and once defined can’t be changed.

But still you can make use of block parameter to conditions to have dynamic query conditions inside associations.

Below line explains how to define dynamic associations :

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>has_one :code_sequence, :class_name => 'Sequence', :conditions => 'kind = "#{self.kind}"'</div></div></pre></div>

Please make a note that below code will not work :

Upgrading from Rails 2.1.x to Rails 2.3.11

Wed, 04 Apr 2012 22:13:00 +0530

If your application is currently on any version of Rails 2.1.x,
Then following changes needs to be done for upgrading your application to Rails 2.3.11

1. First install Rails version 2.3.11

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>gem install rails -v2.3.11</div></div></pre></div>

2. Freeze app ruby gems

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>rake rails:freeze:gems</div></div></pre></div>

Hopefully it should work for you but it gave me following error
> undefined method `manage_gems’ for Gem:Module

3. Create sample rails 2.3.11 app

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>rails 2.3.11 testsapp</div></div></pre></div>

Now, Copy all missing “config/initializers/*” files from newly created “testapp” to the application that is to be upgraded.

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>cp testapp/config/initializers/* config/initializers</div></div></pre></div>

4. Change Rails version inside environment.rb to Rails 2.3.11

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'># Specifies gem version of Rails to use when vendor/rails is not present </div></div><div data-line='2' class='code-highlight-row numbered'><div class='code-highlight-line'>RAILS_GEM_VERSION = '2.3.11'</div></div></pre></div>

5. Rename app/controllers/application.rb file to app/controllers/application_controller.rb

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>rails:update:application_controller</div></div></pre></div>

6. Start rails server and fix the issues one by one

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>ruby script/server</div></div></pre></div>

ruby enumerable & to_proc (ampersond & symbol shortcut)

Thu, 23 Feb 2012 02:09:00 +0530

Basically Enumerable mixin gives collection classes a variety of traverse, search, sort methods.

Understanding ruby blocks

Blocks are statements of code written in ruby. one can take them as similar to c language macro’s

Different ways to define blocks

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>a = proc do </div></div><div data-line='2' class='code-highlight-row numbered'><div class='code-highlight-line'> puts "hello" </div></div><div data-line='3' class='code-highlight-row numbered'><div class='code-highlight-line'>end </div></div><div data-line='4' class='code-highlight-row numbered'><div class='code-highlight-line'>a.call #=> hello </div></div><div data-line='5' class='code-highlight-row numbered'><div class='code-highlight-line'> </div></div><div data-line='6' class='code-highlight-row numbered'><div class='code-highlight-line'>b = lambda do |u| </div></div><div data-line='7' class='code-highlight-row numbered'><div class='code-highlight-line'> puts "hello #{u}" </div></div><div data-line='8' class='code-highlight-row numbered'><div class='code-highlight-line'>end </div></div><div data-line='9' class='code-highlight-row numbered'><div class='code-highlight-line'>b.call('sandip')#=> hello sandip </div></div><div data-line='10' class='code-highlight-row numbered'><div class='code-highlight-line'> </div></div><div data-line='11' class='code-highlight-row numbered'><div class='code-highlight-line'>c = proc {|user| puts user } </div></div><div data-line='12' class='code-highlight-row numbered'><div class='code-highlight-line'>c.call('sandip') #=> sandip</div></div></pre></div>

Passing block to enumerator

Lets assume we have collection array of strings and we want to print it

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>a = ['hi', 'sandip', 'how', 'you', 'doing', '?'] </div></div><div data-line='2' class='code-highlight-row numbered'><div class='code-highlight-line'>=> ["hi", "sandip", "how", "you", "doing", "?"] </div></div><div data-line='3' class='code-highlight-row numbered'><div class='code-highlight-line'> </div></div><div data-line='4' class='code-highlight-row numbered'><div class='code-highlight-line'>a.each {|w| puts w } </div></div><div data-line='5' class='code-highlight-row numbered'><div class='code-highlight-line'> </div></div><div data-line='6' class='code-highlight-row numbered'><div class='code-highlight-line'>q = proc {|w| puts w } </div></div><div data-line='7' class='code-highlight-row numbered'><div class='code-highlight-line'>=> #<Proc:0x00007f9d2be13140@(irb):89> </div></div><div data-line='8' class='code-highlight-row numbered'><div class='code-highlight-line'> </div></div><div data-line='9' class='code-highlight-row numbered'><div class='code-highlight-line'>a.each(&q) #=> </div></div><div data-line='10' class='code-highlight-row numbered'><div class='code-highlight-line'>hi </div></div><div data-line='11' class='code-highlight-row numbered'><div class='code-highlight-line'>sandip </div></div><div data-line='12' class='code-highlight-row numbered'><div class='code-highlight-line'>how </div></div><div data-line='13' class='code-highlight-row numbered'><div class='code-highlight-line'>you </div></div><div data-line='14' class='code-highlight-row numbered'><div class='code-highlight-line'>doing </div></div><div data-line='15' class='code-highlight-row numbered'><div class='code-highlight-line'>? </div></div><div data-line='16' class='code-highlight-row numbered'><div class='code-highlight-line'> </div></div><div data-line='17' class='code-highlight-row numbered'><div class='code-highlight-line'>a.map{|r| q.call(r)} #=> </div></div><div data-line='18' class='code-highlight-row numbered'><div class='code-highlight-line'>hi </div></div><div data-line='19' class='code-highlight-row numbered'><div class='code-highlight-line'>sandip </div></div><div data-line='20' class='code-highlight-row numbered'><div class='code-highlight-line'>how </div></div><div data-line='21' class='code-highlight-row numbered'><div class='code-highlight-line'>you </div></div><div data-line='22' class='code-highlight-row numbered'><div class='code-highlight-line'>doing </div></div><div data-line='23' class='code-highlight-row numbered'><div class='code-highlight-line'>?</div></div></pre></div>

Understanding symbol#to_proc

Symbol has method to_proc which converts symbol to block where symbol is taken as method to be executed on first argument of proc

** How to_proc got implemented inside Symbol class**

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>class Symbol </div></div><div data-line='2' class='code-highlight-row numbered'><div class='code-highlight-line'> def to_proc </div></div><div data-line='3' class='code-highlight-row numbered'><div class='code-highlight-line'> Proc.new { |*args| args.shift.send(self, *args) } </div></div><div data-line='4' class='code-highlight-row numbered'><div class='code-highlight-line'> end </div></div><div data-line='5' class='code-highlight-row numbered'><div class='code-highlight-line'>end</div></div></pre></div>

Lets have some examples:

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>v = :even?.to_proc # equivalent to proc {|a| a.even?} </div></div><div data-line='2' class='code-highlight-row numbered'><div class='code-highlight-line'>#=> #<Proc:0x00007f9d2bddcb90@(irb):97> </div></div><div data-line='3' class='code-highlight-row numbered'><div class='code-highlight-line'>q = [1, 2, 3, 5, 67] </div></div><div data-line='4' class='code-highlight-row numbered'><div class='code-highlight-line'>q.map(&v) => [false, true, false, false, false]</div></div></pre></div>

Is there any shortcut?
Yes, there is shortcut to have block passed to enumerators on the fly using ampersand followed by colon (i.e. symbol)

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>q = [1, 2, 3, 5, 67] </div></div><div data-line='2' class='code-highlight-row numbered'><div class='code-highlight-line'>q.map(&:even?) <=> q.map(&:even?.to_proc) </div></div><div data-line='3' class='code-highlight-row numbered'><div class='code-highlight-line'>q.map(&:even?.to_proc) </div></div><div data-line='4' class='code-highlight-row numbered'><div class='code-highlight-line'>#=> [false, true, false, false, false] </div></div><div data-line='5' class='code-highlight-row numbered'><div class='code-highlight-line'>q.map(&:even?) </div></div><div data-line='6' class='code-highlight-row numbered'><div class='code-highlight-line'>#=> [false, true, false, false, false]</div></div></pre></div>

Some handy examples

<div class='code-highlight'><pre class='code-highlight-pre'><div data-line='1' class='code-highlight-row numbered'><div class='code-highlight-line'>[1, 2, 3, 5, 67].inject(&:+) #=> 78 </div></div><div data-line='2' class='code-highlight-row numbered'><div class='code-highlight-line'>[1, 2, 3, 5, 67].inject(:+) #=> 78 </div></div><div data-line='3' class='code-highlight-row numbered'><div class='code-highlight-line'>[1, 2, 3, 5, 67].any?(&:even?) #=> true </div></div><div data-line='4' class='code-highlight-row numbered'><div class='code-highlight-line'>[1, 2, 3, 5, 67].detect(&:even?) #=> 2 </div></div><div data-line='5' class='code-highlight-row numbered'><div class='code-highlight-line'>['ruby', 'on', 'rails'].map(&:upcase) #=> ["RUBY", "ON", "RAILS"]</div></div></pre></div>