Class: Rails::Railtie

Inherits:
Object show all
Includes:
Initializable
Defined in:
railties/lib/rails/railtie.rb,
railties/lib/rails/railtie/configurable.rb,
railties/lib/rails/railtie/configuration.rb

Overview

Railtie is the core of the Rails framework and provides several hooks to extend Rails and/or modify the initialization process.

Every major component of Rails (Action Mailer, Action Controller, Action View, Active Record and Active Resource) is a Railtie. Each of them is responsible for their own initialization. This makes Rails itself absent of any component hooks, allowing other components to be used in place of any of the Rails defaults.

Developing a Rails extension does not require any implementation of Railtie, but if you need to interact with the Rails framework during or after boot, then Railtie is needed.

For example, an extension doing any of the following would require Railtie:

  • creating initializers

  • configuring a Rails framework for the application, like setting a generator

  • adding config.* keys to the environment

  • setting up a subscriber with ActiveSupport::Notifications

  • adding rake tasks

Creating your Railtie

To extend Rails using Railtie, create a Railtie class which inherits from Rails::Railtie within your extension's namespace. This class must be loaded during the Rails boot process.

The following example demonstrates an extension which can be used with or without Rails.

# lib/my_gem/railtie.rb
module MyGem
  class Railtie < Rails::Railtie
  end
end

# lib/my_gem.rb
require 'my_gem/railtie' if defined?(Rails)

Initializers

To add an initialization step from your Railtie to Rails boot process, you just need to create an initializer block:

class MyRailtie < Rails::Railtie
  initializer "my_railtie.configure_rails_initialization" do
    # some initialization behavior
  end
end

If specified, the block can also receive the application object, in case you need to access some application specific configuration, like middleware:

class MyRailtie < Rails::Railtie
  initializer "my_railtie.configure_rails_initialization" do |app|
    app.middleware.use MyRailtie::Middleware
  end
end

Finally, you can also pass :before and :after as option to initializer, in case you want to couple it with a specific step in the initialization process.

Configuration

Inside the Railtie class, you can access a config object which contains configuration shared by all railties and the application:

class MyRailtie < Rails::Railtie
  # Customize the ORM
  config.app_generators.orm :my_railtie_orm

  # Add a to_prepare block which is executed once in production
  # and before each request in development
  config.to_prepare do
    MyRailtie.setup!
  end
end

Loading rake tasks and generators

If your railtie has rake tasks, you can tell Rails to load them through the method rake_tasks:

class MyRailtie < Rails::Railtie
  rake_tasks do
    load "path/to/my_railtie.tasks"
  end
end

By default, Rails load generators from your load path. However, if you want to place your generators at a different location, you can specify in your Railtie a block which will load them during normal generators lookup:

class MyRailtie < Rails::Railtie
  generators do
    require "path/to/my_railtie_generator"
  end
end

Application, Plugin and Engine

A Rails::Engine is nothing more than a Railtie with some initializers already set. And since Rails::Application and Rails::Plugin are engines, the same configuration described here can be used in all three.

Be sure to look at the documentation of those specific classes for more information.

Defined Under Namespace

Modules: Configurable Classes: Configuration

Constant Summary collapse

ABSTRACT_RAILTIES =
%w(Rails::Railtie Rails::Plugin Rails::Engine Rails::Application)

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Initializable

included, #initializers, #run_initializers

Class Method Details

.abstract_railtie?Boolean

Returns:

  • (Boolean)

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# File 'railties/lib/rails/railtie.rb', line 154

def abstract_railtie?
  ABSTRACT_RAILTIES.include?(name)
end

.console(&blk) ⇒ Object


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# File 'railties/lib/rails/railtie.rb', line 142

def console(&blk)
  @load_console ||= []
  @load_console << blk if blk
  @load_console
end

.generators(&blk) ⇒ Object


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# File 'railties/lib/rails/railtie.rb', line 148

def generators(&blk)
  @generators ||= []
  @generators << blk if blk
  @generators
end

.inherited(base) ⇒ Object


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# File 'railties/lib/rails/railtie.rb', line 129

def inherited(base)
  unless base.abstract_railtie?
    base.send(:include, Railtie::Configurable)
    subclasses << base
  end
end

.railtie_name(name = nil) ⇒ Object


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# File 'railties/lib/rails/railtie.rb', line 158

def railtie_name(name = nil)
  @railtie_name = name.to_s if name
  @railtie_name ||= generate_railtie_name(self.name)
end

.rake_tasks(&blk) ⇒ Object


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# File 'railties/lib/rails/railtie.rb', line 136

def rake_tasks(&blk)
  @rake_tasks ||= []
  @rake_tasks << blk if blk
  @rake_tasks
end

.subclassesObject


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# File 'railties/lib/rails/railtie.rb', line 125

def subclasses
  @subclasses ||= []
end

Instance Method Details

#configObject


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# File 'railties/lib/rails/railtie.rb', line 171

def config
  @config ||= Railtie::Configuration.new
end

#eager_load!Object


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# File 'railties/lib/rails/railtie.rb', line 175

def eager_load!
end

#load_console(app = self) ⇒ Object


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# File 'railties/lib/rails/railtie.rb', line 178

def load_console(app=self)
  self.class.console.each { |block| block.call(app) }
end

#load_generators(app = self) ⇒ Object


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# File 'railties/lib/rails/railtie.rb', line 194

def load_generators(app=self)
  self.class.generators.each { |block| block.call(app) }
end

#load_tasks(app = self) ⇒ Object


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# File 'railties/lib/rails/railtie.rb', line 182

def load_tasks(app=self)
  extend Rake::DSL if defined? Rake::DSL
  self.class.rake_tasks.each { |block| self.instance_exec(app, &block) }

  # load also tasks from all superclasses
  klass = self.class.superclass
  while klass.respond_to?(:rake_tasks)
    klass.rake_tasks.each { |t| self.instance_exec(app, &t) }
    klass = klass.superclass
  end
end

#railtie_namespaceObject


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# File 'railties/lib/rails/railtie.rb', line 198

def railtie_namespace
  @railtie_namespace ||= self.class.parents.detect { |n| n.respond_to?(:railtie_namespace) }
end