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 and Active Record) 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 and Engine

A Rails::Engine is nothing more than a Railtie with some initializers already set. And since Rails::Application is an engine, the same configuration described here can be used in both.

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

Defined Under Namespace

Modules: Configurable Classes: Configuration

Constant Summary

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

Class Method Summary (collapse)

Instance Method Summary (collapse)

Methods included from Initializable

included, #initializers, #run_initializers

Constructor Details

- (Railtie) initialize



203
204
205
206
207
# File 'railties/lib/rails/railtie.rb', line 203

def initialize
  if self.class.abstract_railtie?
    raise "#{self.class.name} is abstract, you cannot instantiate it directly."
  end
end

Class Method Details

+ (Boolean) abstract_railtie?



159
160
161
# File 'railties/lib/rails/railtie.rb', line 159

def abstract_railtie?
  ABSTRACT_RAILTIES.include?(name)
end

+ (Object) configure(&block)

Allows you to configure the railtie. This is the same method seen in Railtie::Configurable, but this module is no longer required for all subclasses of Railtie so we provide the class method here.



181
182
183
# File 'railties/lib/rails/railtie.rb', line 181

def configure(&block)
  instance.configure(&block)
end

+ (Object) console(&blk)



141
142
143
144
145
# File 'railties/lib/rails/railtie.rb', line 141

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

+ (Object) generators(&blk)



153
154
155
156
157
# File 'railties/lib/rails/railtie.rb', line 153

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

+ (Object) inherited(base)



129
130
131
132
133
# File 'railties/lib/rails/railtie.rb', line 129

def inherited(base)
  unless base.abstract_railtie?
    subclasses << base
  end
end

+ (Object) instance

Since Rails::Railtie cannot be instantiated, any methods that call instance are intended to be called only on subclasses of a Railtie.



170
171
172
# File 'railties/lib/rails/railtie.rb', line 170

def instance
  @instance ||= new
end

+ (Object) railtie_name(name = nil)



163
164
165
166
# File 'railties/lib/rails/railtie.rb', line 163

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

+ (Object) rake_tasks(&blk)



135
136
137
138
139
# File 'railties/lib/rails/railtie.rb', line 135

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

+ (Boolean) respond_to_missing?(*args)



174
175
176
# File 'railties/lib/rails/railtie.rb', line 174

def respond_to_missing?(*args)
  instance.respond_to?(*args) || super
end

+ (Object) runner(&blk)



147
148
149
150
151
# File 'railties/lib/rails/railtie.rb', line 147

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

+ (Object) subclasses



125
126
127
# File 'railties/lib/rails/railtie.rb', line 125

def subclasses
  @subclasses ||= []
end

Instance Method Details

- (Object) config



213
214
215
# File 'railties/lib/rails/railtie.rb', line 213

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

- (Object) configure(&block)



209
210
211
# File 'railties/lib/rails/railtie.rb', line 209

def configure(&block)
  instance_eval(&block)
end

- (Object) railtie_namespace



217
218
219
# File 'railties/lib/rails/railtie.rb', line 217

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