require 'rails/initializable'
require 'rails/configuration'
require 'active_support/inflector'
require 'active_support/core_ext/module/introspection'
require 'active_support/core_ext/module/delegation'
module Rails
# 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 <tt>config.*</tt> 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 <tt>:before</tt> and <tt>:after</tt> 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 loads 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.
#
class Railtie
autoload :Configuration, "rails/railtie/configuration"
include Initializable
ABSTRACT_RAILTIES = %w(Rails::Railtie Rails::Engine Rails::Application)
class << self
private :new
delegate :config, to: :instance
def subclasses
@subclasses ||= []
end
def inherited(base)
unless base.abstract_railtie?
subclasses << base
end
end
def rake_tasks(&blk)
@rake_tasks ||= []
@rake_tasks << blk if blk
@rake_tasks
end
def console(&blk)
@load_console ||= []
@load_console << blk if blk
@load_console
end
def runner(&blk)
@load_runner ||= []
@load_runner << blk if blk
@load_runner
end
def generators(&blk)
@generators ||= []
@generators << blk if blk
@generators
end
def abstract_railtie?
ABSTRACT_RAILTIES.include?(name)
end
def railtie_name(name = nil)
@railtie_name = name.to_s if name
@railtie_name ||= generate_railtie_name(self.name)
end
# Since Rails::Railtie cannot be instantiated, any methods that call
# +instance+ are intended to be called only on subclasses of a Railtie.
def instance
@instance ||= new
end
def respond_to_missing?(*args)
instance.respond_to?(*args) || super
end
# 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.
def configure(&block)
instance.configure(&block)
end
protected
def generate_railtie_name(string) #:nodoc:
ActiveSupport::Inflector.underscore(string).tr("/", "_")
end
# If the class method does not have a method, then send the method call
# to the Railtie instance.
def method_missing(name, *args, &block)
if instance.respond_to?(name)
instance.public_send(name, *args, &block)
else
super
end
end
end
delegate :railtie_name, to: :class
def initialize #:nodoc:
if self.class.abstract_railtie?
raise "#{self.class.name} is abstract, you cannot instantiate it directly."
end
end
def configure(&block) #:nodoc:
instance_eval(&block)
end
# This is used to create the <tt>config</tt> object on Railties, an instance of
# Railtie::Configuration, that is used by Railties and Application to store
# related configuration.
def config
@config ||= Railtie::Configuration.new
end
def railtie_namespace #:nodoc:
@railtie_namespace ||= self.class.parents.detect { |n| n.respond_to?(:railtie_namespace) }
end
protected
def run_console_blocks(app) #:nodoc:
each_registered_block(:console) { |block| block.call(app) }
end
def run_generators_blocks(app) #:nodoc:
each_registered_block(:generators) { |block| block.call(app) }
end
def run_runner_blocks(app) #:nodoc:
each_registered_block(:runner) { |block| block.call(app) }
end
def run_tasks_blocks(app) #:nodoc:
extend Rake::DSL
each_registered_block(:rake_tasks) { |block| instance_exec(app, &block) }
end
private
def each_registered_block(type, &block)
klass = self.class
while klass.respond_to?(type)
klass.public_send(type).each(&block)
klass = klass.superclass
end
end
end
end
