1. Install rvm

2. From your rails project, install your gems to vendor/bundle

    bundle install --path vendor/bundle
   

3. In your rails project, there will be a file called .bundle/config created which will have:

    ---
    BUNDLE_PATH: vendor/bundle
    BUNDLE_DISABLE_SHARED_GEMS: '1'
   

4. Start rails from script/rails which will use gems from vendor/bundle:

    script/rails s
   

NOTE: The above is similar to Python's virtualenv in isolating specific library versions to a specific location

1. Starts a new project:

    rails project -d postgresql
   

2. Configure your database connection settings, edit:

    project/config/database.yml
   

3. Create your database:

    rake db:create
   

4. Generate controller:

    rails generate controller home index
   

5. Scaffold:

    rails generate scaffold Post name:string title:string content:text
   

6. The types supported by Active Record are

    :primary_key, :string, :text, :integer, :float, :decimal, :datetime, 
    :timestamp, :time, :date, :binary, :boolean</pre>
   

7. Run a specific unit test from your project folder:

    rake test:units TEST=test/unit/your_model_test.rb
   

8. Check for pending migrations:

    rake db:abort_if_pending_migrations
   

9. Generate a migration stub file:

    rails generate migration AddCityToPerson
   

10. Load all fixtures:

     rake db:fixtures:load
    

11. Load a specific fixture

     rake db:fixtures:load FIXTURES=your_fix.yml
    

12. View all routes

     rake routes
    

13. Run a script under the Rails environment where test.rb is at the project root folder:

     script/rails runner "eval(File.read 'test.rb')"
    

14. Rake under a specific environment:

     rake db:schema:load RAILS_ENV=staging
    

15. Running the console under a custom staging environment:

     script/rails c staging
    

1. Scaffold the User

    rails generate scaffold User name:string hashed_password:string salt:string
   

2. Create app/controllers/admin_controller.rb

    class AdminController < ApplicationController
      before_filter :authenticate, :except => :login
   
      def login
        session[:user_id] = nil
        if request.post?
          user = User.authenticate(params[:name], params[:password])
          if user
            session[:user_id] = user.id
            uri = session[:original_uri]
            session[:original_uri] = nil
            redirect_to(uri || { :action => 'index' })
          else
            flash.now[:notice] = 'Invalid user/password combination'
          end
        end
      end
   
      def logout
        session[:user_id] = :logged_out
        flash[:notice] = "Logged out"
        redirect_to(:action => "login")
      end
    end
   

3. Add the following to app/controllers/application_controller.rb

    class ApplicationController < ActionController::Base
      before_filter :authenticate, :except => [:index, :show]
      protect_from_forgery
   
    protected
      def authenticate
        unless User.find_by_id(session[:user_id])
          session[:original_uri] = request.request_uri
          flash[:notice] = 'Please log in'
          redirect_to :controller => 'admin', :action => 'login'
        end
      end
    end
   

4. User model app/models/user.rb

    require 'digest/sha1'
   
    class User < ActiveRecord::Base
      validates_presence_of :name
      validates_uniqueness_of :name
   
      attr_accessor :password_confirmation
      validates_confirmation_of :password
      validate :password_non_blank
   
      def self.authenticate(name, password)
        user = self.find_by_name(name)
        if user
          expected_password = encrypted_password(password, user.salt)
          if user.hashed_password != expected_password
            user = nil
          end
        end
        user
      end
   
      # 'password' is a virtual attribute
      def password
        @password
      end
   
      def password=(pwd)
        @password = pwd
        return if pwd.blank?
        create_new_salt
        self.hashed_password = User.encrypted_password(self.password, self.salt)
      end
   
    private
      def password_non_blank
        errors.add(:password, 'Missing password') if hashed_password.blank?
      end
   
      def self.encrypted_password(password, salt)
        string_to_hash = password + 'wibble' + salt
        Digest::SHA1.hexdigest(string_to_hash)
      end
   
      def create_new_salt
        self.salt = self.object_id.to_s + rand.to_s
      end
    end
   

5. Update your config/routes.rb

    match 'admin' => 'admin#index'
    match 'login' => 'admin#login', :as => 'login'
    match 'logout' => 'admin#logout'
   

6. Login view app/views/admin/login.html.erb

    <div class="depot-form">
      <% form_tag(login_path, :method => "post") do %>
        <fieldset>
          <legend>Please Log In</legend>
          <div>
            <label for="name">Name:</label>
            <%= text_field_tag :name, params[:name] %>
          </div>
   
          <div>
            <label for="password">Password:</label>
            <%= password_field_tag :password, params[:password] %>
          </div>
   
          <div>
            <%= submit_tag "Login" %>
          </div>
        </fieldset>
      <% end %>
    </div>