Rails plugins

Generate a plugin

Generate a Rails Engine plugin:

rails plugin new myplugin --skip-bundle --full

Initializers

• Rails::Railtie
• EngineYard blog post

Subclass Railtie and provide an initializer method.

module NewPlugin
  class Railtie < Rails::Railtie
    initializer "newplugin.initialize" do |app|
 
      # subscribe to all rails notifications: controllers, AR, etc.
      ActiveSupport::Notifications.subscribe do |*args|
        event = ActiveSupport::Notifications::Event.new(*args)
        puts "Got notification: #{event.inspect}"
      end
 
    end
  end
end

Custom routes

• ActionDispatch::Routing::Mapper

To create custom routes.rb keywords:

# # routes.rb:
# myplugin_for x
#
class ActionDispatch::Routing
  class Mapper
    def myplugin_for(*x)
    end
  end
end

Example with a block:

# authenticated do
#   resources :users
# end
#
def authenticated
  constraint = lambda { |request| request... }

  constraints(constraint) { yield }
end

Custom generators

• Guide: generators
• ActiveRecord::Generators::Base

Basic

# rails g initializer
# lib/generators/initializer_generator.rb
class InitializerGenerator < Rails::Generators::Base
  def create_initializer_file
    create_file "config/initializers/initializer.rb", "# Add initialization content here"
  end
end

• Extend Rails::Generators::Base.
• Each public method in the generator is executed when a generator is invoked.

Generating a generator

$ rails generate generator initializer

NamedBase

Use NamedBase instead if you want to take an argument. It will be available as file_name.

class InitializerGenerator < Rails::Generators::Base
  def lol
    puts file_name
  end
end

More

class InitializerGenerator < Rails::Generators::NamedBase
  # 
  source_root File.expand_path("../templates", __FILE__)
  desc "Description goes here."
end

Generators lookup

When invoking rails g XXX:

[rails/]generators/XXX/XXX_generator.rb
[rails/]generators/XXX_generator.rb

When invoking rails g XXX:YYY:

[rails/]generators/XXX/YYY_generator.rb

ActiveModel ‘acts as’

# yaffle/lib/yaffle/acts_as_yaffle.rb
module Yaffle
  module ActsAsYaffle
    extend ActiveSupport::Concern
 
    included do
    end
 
    module ClassMethods
      def acts_as_yaffle(options = {})
        # your code will go here
      end
    end
  end
end
 
ActiveRecord::Base.send :include, Yaffle::ActsAsYaffle