Class: Rails::Railtie
- Inherits:
-
Object
- Object
- Rails::Railtie
- Includes:
- Initializable
- Defined in:
- lib/rails/railtie.rb,
lib/rails/railtie/configurable.rb,
lib/rails/railtie/configuration.rb
Overview
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, Active Record, etc.) implements 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 implementing a railtie, but if you need to interact with the Rails framework during or after boot, then a railtie is needed.
For example, an extension doing any of the following would need a 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 a Railtie
To extend Rails using a railtie, create a subclass of Rails::Railtie
. This class must be loaded during the Rails boot process, and is conventionally called MyNamespace::Railtie
.
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 to the Rails boot process from your railtie, just define the initialization code with the initializer
macro:
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 options to initializer
, in case you want to couple it with a specific step in the initialization process.
Configuration
Railties 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
An 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.
Direct Known Subclasses
Defined Under Namespace
Modules: Configurable Classes: Configuration
Constant Summary collapse
- ABSTRACT_RAILTIES =
%w(Rails::Railtie Rails::Engine Rails::Application)
Class Method Summary collapse
- .abstract_railtie? ⇒ Boolean
-
.configure(&block) ⇒ Object
Allows you to configure the railtie.
- .console(&blk) ⇒ Object
- .generators(&blk) ⇒ Object
- .inherited(base) ⇒ Object
-
.instance ⇒ Object
Since Rails::Railtie cannot be instantiated, any methods that call
instance
are intended to be called only on subclasses of a Railtie. - .railtie_name(name = nil) ⇒ Object
- .rake_tasks(&blk) ⇒ Object
- .respond_to_missing?(*args) ⇒ Boolean
- .runner(&blk) ⇒ Object
- .subclasses ⇒ Object
Instance Method Summary collapse
-
#config ⇒ Object
This is used to create the
config
object on Railties, an instance of Railtie::Configuration, that is used by Railties and Application to store related configuration. -
#configure(&block) ⇒ Object
:nodoc:.
-
#initialize ⇒ Railtie
constructor
:nodoc:.
-
#railtie_namespace ⇒ Object
:nodoc:.
Methods included from Initializable
included, #initializers, #run_initializers
Constructor Details
#initialize ⇒ Railtie
:nodoc:
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# File 'lib/rails/railtie.rb', line 202 def initialize #:nodoc: if self.class.abstract_railtie? raise "#{self.class.name} is abstract, you cannot instantiate it directly." end end |
Class Method Details
.abstract_railtie? ⇒ Boolean
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# File 'lib/rails/railtie.rb', line 158 def abstract_railtie? ABSTRACT_RAILTIES.include?(name) end |
.configure(&block) ⇒ Object
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.
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# File 'lib/rails/railtie.rb', line 180 def configure(&block) instance.configure(&block) end |
.console(&blk) ⇒ Object
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# File 'lib/rails/railtie.rb', line 140 def console(&blk) @load_console ||= [] @load_console << blk if blk @load_console end |
.generators(&blk) ⇒ Object
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# File 'lib/rails/railtie.rb', line 152 def generators(&blk) @generators ||= [] @generators << blk if blk @generators end |
.inherited(base) ⇒ Object
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# File 'lib/rails/railtie.rb', line 128 def inherited(base) unless base.abstract_railtie? subclasses << base end end |
.instance ⇒ Object
Since Rails::Railtie cannot be instantiated, any methods that call instance
are intended to be called only on subclasses of a Railtie.
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# File 'lib/rails/railtie.rb', line 169 def instance @instance ||= new end |
.railtie_name(name = nil) ⇒ Object
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# File 'lib/rails/railtie.rb', line 162 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 'lib/rails/railtie.rb', line 134 def rake_tasks(&blk) @rake_tasks ||= [] @rake_tasks << blk if blk @rake_tasks end |
.respond_to_missing?(*args) ⇒ Boolean
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# File 'lib/rails/railtie.rb', line 173 def respond_to_missing?(*args) instance.respond_to?(*args) || super end |
.runner(&blk) ⇒ Object
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# File 'lib/rails/railtie.rb', line 146 def runner(&blk) @load_runner ||= [] @load_runner << blk if blk @load_runner end |
.subclasses ⇒ Object
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# File 'lib/rails/railtie.rb', line 124 def subclasses @subclasses ||= [] end |
Instance Method Details
#config ⇒ Object
This is used to create the config
object on Railties, an instance of Railtie::Configuration, that is used by Railties and Application to store related configuration.
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# File 'lib/rails/railtie.rb', line 215 def config @config ||= Railtie::Configuration.new end |
#configure(&block) ⇒ Object
:nodoc:
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# File 'lib/rails/railtie.rb', line 208 def configure(&block) #:nodoc: instance_eval(&block) end |
#railtie_namespace ⇒ Object
:nodoc:
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# File 'lib/rails/railtie.rb', line 219 def railtie_namespace #:nodoc: @railtie_namespace ||= self.class.parents.detect { |n| n.respond_to?(:railtie_namespace) } end |