require 'rails/railtie' require 'active_support/core_ext/module/delegation' require 'pathname' require 'rbconfig' require 'rails/engine/railties' module Rails # <tt>Rails::Engine</tt> allows you to wrap a specific Rails application or subset of # functionality and share it with other applications. Since Rails 3.0, every # <tt>Rails::Application</tt> is just an engine, which allows for simple # feature and application sharing. # # Any <tt>Rails::Engine</tt> is also a <tt>Rails::Railtie</tt>, so the same # methods (like <tt>rake_tasks</tt> and +generators+) and configuration # options that are available in railties can also be used in engines. # # == Creating an Engine # # In Rails versions prior to 3.0, your gems automatically behaved as engines, however, # this coupled Rails to Rubygems. Since Rails 3.0, if you want a gem to automatically # behave as an engine, you have to specify an +Engine+ for it somewhere inside # your plugin's +lib+ folder (similar to how we specify a +Railtie+): # # # lib/my_engine.rb # module MyEngine # class Engine < Rails::Engine # end # end # # Then ensure that this file is loaded at the top of your <tt>config/application.rb</tt> # (or in your +Gemfile+) and it will automatically load models, controllers and helpers # inside +app+, load routes at <tt>config/routes.rb</tt>, load locales at # <tt>config/locales/*</tt>, and load tasks at <tt>lib/tasks/*</tt>. # # == Configuration # # Besides the +Railtie+ configuration which is shared across the application, in a # <tt>Rails::Engine</tt> you can access <tt>autoload_paths</tt>, <tt>eager_load_paths</tt> # and <tt>autoload_once_paths</tt>, which, differently from a <tt>Railtie</tt>, are scoped to # the current engine. # # Example: # # class MyEngine < Rails::Engine # # Add a load path for this specific Engine # config.autoload_paths << File.expand_path("../lib/some/path", __FILE__) # # initializer "my_engine.add_middleware" do |app| # app.middleware.use MyEngine::Middleware # end # end # # == Generators # # You can set up generators for engines with <tt>config.generators</tt> method: # # class MyEngine < Rails::Engine # config.generators do |g| # g.orm :active_record # g.template_engine :erb # g.test_framework :test_unit # end # end # # You can also set generators for an application by using <tt>config.app_generators</tt>: # # class MyEngine < Rails::Engine # # note that you can also pass block to app_generators in the same way you # # can pass it to generators method # config.app_generators.orm :datamapper # end # # == Paths # # Since Rails 3.0, applications and engines have more flexible path configuration (as # opposed to the previous hardcoded path configuration). This means that you are not # required to place your controllers at <tt>app/controllers</tt>, but in any place # which you find convenient. # # For example, let's suppose you want to place your controllers in <tt>lib/controllers</tt>. # You can set that as an option: # # class MyEngine < Rails::Engine # paths["app/controllers"] = "lib/controllers" # end # # You can also have your controllers loaded from both <tt>app/controllers</tt> and # <tt>lib/controllers</tt>: # # class MyEngine < Rails::Engine # paths["app/controllers"] << "lib/controllers" # end # # The available paths in an engine are: # # class MyEngine < Rails::Engine # paths["app"] # => ["app"] # paths["app/controllers"] # => ["app/controllers"] # paths["app/helpers"] # => ["app/helpers"] # paths["app/models"] # => ["app/models"] # paths["app/views"] # => ["app/views"] # paths["lib"] # => ["lib"] # paths["lib/tasks"] # => ["lib/tasks"] # paths["config"] # => ["config"] # paths["config/initializers"] # => ["config/initializers"] # paths["config/locales"] # => ["config/locales"] # paths["config/routes"] # => ["config/routes.rb"] # end # # The <tt>Application</tt> class adds a couple more paths to this set. And as in your # <tt>Application</tt>, all folders under +app+ are automatically added to the load path. # If you have an <tt>app/observers</tt> folder for example, it will be added by default. # # == Endpoint # # An engine can be also a rack application. It can be useful if you have a rack application that # you would like to wrap with +Engine+ and provide some of the +Engine+'s features. # # To do that, use the +endpoint+ method: # # module MyEngine # class Engine < Rails::Engine # endpoint MyRackApplication # end # end # # Now you can mount your engine in application's routes just like that: # # MyRailsApp::Application.routes.draw do # mount MyEngine::Engine => "/engine" # end # # == Middleware stack # # As an engine can now be a rack endpoint, it can also have a middleware # stack. The usage is exactly the same as in <tt>Application</tt>: # # module MyEngine # class Engine < Rails::Engine # middleware.use SomeMiddleware # end # end # # == Routes # # If you don't specify an endpoint, routes will be used as the default # endpoint. You can use them just like you use an application's routes: # # # ENGINE/config/routes.rb # MyEngine::Engine.routes.draw do # match "/" => "posts#index" # end # # == Mount priority # # Note that now there can be more than one router in your application, and it's better to avoid # passing requests through many routers. Consider this situation: # # MyRailsApp::Application.routes.draw do # mount MyEngine::Engine => "/blog" # match "/blog/omg" => "main#omg" # end # # +MyEngine+ is mounted at <tt>/blog</tt>, and <tt>/blog/omg</tt> points to application's # controller. In such a situation, requests to <tt>/blog/omg</tt> will go through +MyEngine+, # and if there is no such route in +Engine+'s routes, it will be dispatched to <tt>main#omg</tt>. # It's much better to swap that: # # MyRailsApp::Application.routes.draw do # match "/blog/omg" => "main#omg" # mount MyEngine::Engine => "/blog" # end # # Now, +Engine+ will get only requests that were not handled by +Application+. # # == Engine name # # There are some places where an Engine's name is used: # # * routes: when you mount an Engine with <tt>mount(MyEngine::Engine => '/my_engine')</tt>, # it's used as default :as option # * some of the rake tasks are based on engine name, e.g. <tt>my_engine:install:migrations</tt>, # <tt>my_engine:install:assets</tt> # # Engine name is set by default based on class name. For <tt>MyEngine::Engine</tt> it will be # <tt>my_engine_engine</tt>. You can change it manually using the <tt>engine_name</tt> method: # # module MyEngine # class Engine < Rails::Engine # engine_name "my_engine" # end # end # # == Isolated Engine # # Normally when you create controllers, helpers and models inside an engine, they are treated # as if they were created inside the application itself. This means that all helpers and # named routes from the application will be available to your engine's controllers as well. # # However, sometimes you want to isolate your engine from the application, especially if your engine # has its own router. To do that, you simply need to call +isolate_namespace+. This method requires # you to pass a module where all your controllers, helpers and models should be nested to: # # module MyEngine # class Engine < Rails::Engine # isolate_namespace MyEngine # end # end # # With such an engine, everything that is inside the +MyEngine+ module will be isolated from # the application. # # Consider such controller: # # module MyEngine # class FooController < ActionController::Base # end # end # # If an engine is marked as isolated, +FooController+ has access only to helpers from +Engine+ and # <tt>url_helpers</tt> from <tt>MyEngine::Engine.routes</tt>. # # The next thing that changes in isolated engines is the behavior of routes. Normally, when you namespace # your controllers, you also need to do namespace all your routes. With an isolated engine, # the namespace is applied by default, so you can ignore it in routes: # # MyEngine::Engine.routes.draw do # resources :articles # end # # The routes above will automatically point to <tt>MyEngine::ApplicationController</tt>. Furthermore, you don't # need to use longer url helpers like <tt>my_engine_articles_path</tt>. Instead, you should simply use # <tt>articles_path</tt> as you would do with your application. # # To make that behavior consistent with other parts of the framework, an isolated engine also has influence on # <tt>ActiveModel::Naming</tt>. When you use a namespaced model, like <tt>MyEngine::Article</tt>, it will normally # use the prefix "my_engine". In an isolated engine, the prefix will be omitted in url helpers and # form fields for convenience. # # polymorphic_url(MyEngine::Article.new) # => "articles_path" # # form_for(MyEngine::Article.new) do # text_field :title # => <input type="text" name="article[title]" id="article_title" /> # end # # Additionally, an isolated engine will set its name according to namespace, so # MyEngine::Engine.engine_name will be "my_engine". It will also set MyEngine.table_name_prefix # to "my_engine_", changing the MyEngine::Article model to use the my_engine_articles table. # # == Using Engine's routes outside Engine # # Since you can now mount an engine inside application's routes, you do not have direct access to +Engine+'s # <tt>url_helpers</tt> inside +Application+. When you mount an engine in an application's routes, a special helper is # created to allow you to do that. Consider such a scenario: # # # config/routes.rb # MyApplication::Application.routes.draw do # mount MyEngine::Engine => "/my_engine", :as => "my_engine" # match "/foo" => "foo#index" # end # # Now, you can use the <tt>my_engine</tt> helper inside your application: # # class FooController < ApplicationController # def index # my_engine.root_url #=> /my_engine/ # end # end # # There is also a <tt>main_app</tt> helper that gives you access to application's routes inside Engine: # # module MyEngine # class BarController # def index # main_app.foo_path #=> /foo # end # end # end # # Note that the <tt>:as</tt> option given to mount takes the <tt>engine_name</tt> as default, so most of the time # you can simply omit it. # # Finally, if you want to generate a url to an engine's route using # <tt>polymorphic_url</tt>, you also need to pass the engine helper. Let's # say that you want to create a form pointing to one of the engine's routes. # All you need to do is pass the helper as the first element in array with # attributes for url: # # form_for([my_engine, @user]) # # This code will use <tt>my_engine.user_path(@user)</tt> to generate the proper route. # # == Isolated engine's helpers # # Sometimes you may want to isolate engine, but use helpers that are defined for it. # If you want to share just a few specific helpers you can add them to application's # helpers in ApplicationController: # # class ApplicationController < ActionController::Base # helper MyEngine::SharedEngineHelper # end # # If you want to include all of the engine's helpers, you can use #helpers method on an engine's # instance: # # class ApplicationController < ActionController::Base # helper MyEngine::Engine.helpers # end # # It will include all of the helpers from engine's directory. Take into account that this does # not include helpers defined in controllers with helper_method or other similar solutions, # only helpers defined in the helpers directory will be included. # # == Migrations & seed data # # Engines can have their own migrations. The default path for migrations is exactly the same # as in application: <tt>db/migrate</tt> # # To use engine's migrations in application you can use rake task, which copies them to # application's dir: # # rake ENGINE_NAME:install:migrations # # Note that some of the migrations may be skipped if a migration with the same name already exists # in application. In such a situation you must decide whether to leave that migration or rename the # migration in the application and rerun copying migrations. # # If your engine has migrations, you may also want to prepare data for the database in # the <tt>seeds.rb</tt> file. You can load that data using the <tt>load_seed</tt> method, e.g. # # MyEngine::Engine.load_seed # # == Loading priority # # In order to change engine's priority you can use config.railties_order in main application. # It will affect the priority of loading views, helpers, assets and all the other files # related to engine or application. # # Example: # # # load Blog::Engine with highest priority, followed by application and other railties # config.railties_order = [Blog::Engine, :main_app, :all] # class Engine < Railtie autoload :Configuration, "rails/engine/configuration" autoload :Railties, "rails/engine/railties" def load_generators(app=self) initialize_generators railties.all { |r| r.load_generators(app) } Rails::Generators.configure!(app.config.generators) super self end class << self attr_accessor :called_from, :isolated alias :isolated? :isolated alias :engine_name :railtie_name def inherited(base) unless base.abstract_railtie? base.called_from = begin # Remove the line number from backtraces making sure we don't leave anything behind call_stack = caller.map { |p| p.sub(/:\d+.*/, '') } File.dirname(call_stack.detect { |p| p !~ %r[railties[\w.-]*/lib/rails|rack[\w.-]*/lib/rack] }) end end super end def endpoint(endpoint = nil) @endpoint ||= nil @endpoint = endpoint if endpoint @endpoint end def isolate_namespace(mod) engine_name(generate_railtie_name(mod)) self.routes.default_scope = { :module => ActiveSupport::Inflector.underscore(mod.name) } self.isolated = true unless mod.respond_to?(:railtie_namespace) name, railtie = engine_name, self mod.singleton_class.instance_eval do define_method(:railtie_namespace) { railtie } unless mod.respond_to?(:table_name_prefix) define_method(:table_name_prefix) { "#{name}_" } end unless mod.respond_to?(:use_relative_model_naming?) class_eval "def use_relative_model_naming?; true; end", __FILE__, __LINE__ end unless mod.respond_to?(:railtie_helpers_paths) define_method(:railtie_helpers_paths) { railtie.helpers_paths } end unless mod.respond_to?(:railtie_routes_url_helpers) define_method(:railtie_routes_url_helpers) { railtie.routes_url_helpers } end end end end # Finds engine with given path def find(path) expanded_path = File.expand_path path.to_s Rails::Engine::Railties.engines.find { |engine| File.expand_path(engine.root.to_s) == expanded_path } end end delegate :middleware, :root, :paths, :to => :config delegate :engine_name, :isolated?, :to => "self.class" def load_tasks(app=self) railties.all { |r| r.load_tasks(app) } super paths["lib/tasks"].existent.sort.each { |ext| load(ext) } end def load_console(app=self) railties.all { |r| r.load_console(app) } super end def load_runner(app=self) railties.all { |r| r.load_runner(app) } super end def eager_load! railties.all(&:eager_load!) config.eager_load_paths.each do |load_path| matcher = /\A#{Regexp.escape(load_path)}\/(.*)\.rb\Z/ Dir.glob("#{load_path}/**/*.rb").sort.each do |file| require_dependency file.sub(matcher, '\1') end end end def railties @railties ||= self.class::Railties.new(config) end def helpers @helpers ||= begin helpers = Module.new all = ActionController::Base.all_helpers_from_path(helpers_paths) ActionController::Base.modules_for_helpers(all).each do |mod| helpers.send(:include, mod) end helpers end end def helpers_paths paths["app/helpers"].existent end def routes_url_helpers routes.url_helpers end def app @app ||= begin config.middleware = config.middleware.merge_into(default_middleware_stack) config.middleware.build(endpoint) end end def endpoint self.class.endpoint || routes end def call(env) app.call(env.merge!(env_config)) end def env_config @env_config ||= { 'action_dispatch.routes' => routes } end def routes @routes ||= ActionDispatch::Routing::RouteSet.new @routes.append(&Proc.new) if block_given? @routes end def ordered_railties railties.all + [self] end def initializers initializers = [] ordered_railties.each do |r| if r == self initializers += super else initializers += r.initializers end end initializers end def config @config ||= Engine::Configuration.new(find_root_with_flag("lib")) end # Load data from db/seeds.rb file. It can be used in to load engines' # seeds, e.g.: # # Blog::Engine.load_seed def load_seed seed_file = paths["db/seeds"].existent.first load(seed_file) if seed_file end # Add configured load paths to ruby load paths and remove duplicates. initializer :set_load_path, :before => :bootstrap_hook do _all_load_paths.reverse_each do |path| $LOAD_PATH.unshift(path) if File.directory?(path) end $LOAD_PATH.uniq! end # Set the paths from which Rails will automatically load source files, # and the load_once paths. # # This needs to be an initializer, since it needs to run once # per engine and get the engine as a block parameter initializer :set_autoload_paths, :before => :bootstrap_hook do |app| ActiveSupport::Dependencies.autoload_paths.unshift(*_all_autoload_paths) ActiveSupport::Dependencies.autoload_once_paths.unshift(*_all_autoload_once_paths) # Freeze so future modifications will fail rather than do nothing mysteriously config.autoload_paths.freeze config.eager_load_paths.freeze config.autoload_once_paths.freeze end initializer :add_routing_paths do |app| paths = self.paths["config/routes"].existent if routes? || paths.any? app.routes_reloader.paths.unshift(*paths) app.routes_reloader.route_sets << routes end end # I18n load paths are a special case since the ones added # later have higher priority. initializer :add_locales do config.i18n.railties_load_path.concat(paths["config/locales"].existent) end initializer :add_view_paths do views = paths["app/views"].existent unless views.empty? ActiveSupport.on_load(:action_controller){ prepend_view_path(views) } ActiveSupport.on_load(:action_mailer){ prepend_view_path(views) } end end initializer :load_environment_config, :before => :load_environment_hook, :group => :all do environment = paths["config/environments"].existent.first require environment if environment end initializer :append_assets_path, :group => :all do |app| app.config.assets.paths.unshift(*paths["vendor/assets"].existent_directories) app.config.assets.paths.unshift(*paths["lib/assets"].existent_directories) app.config.assets.paths.unshift(*paths["app/assets"].existent_directories) end initializer :prepend_helpers_path do |app| if !isolated? || (app == self) app.config.helpers_paths.unshift(*paths["app/helpers"].existent) end end initializer :load_config_initializers do config.paths["config/initializers"].existent.sort.each do |initializer| load(initializer) end end initializer :engines_blank_point do # We need this initializer so all extra initializers added in engines are # consistently executed after all the initializers above across all engines. end rake_tasks do next if self.is_a?(Rails::Application) next unless has_migrations? namespace railtie_name do namespace :install do desc "Copy migrations from #{railtie_name} to application" task :migrations do ENV["FROM"] = railtie_name Rake::Task["railties:install:migrations"].invoke end end end end protected def initialize_generators require "rails/generators" end def routes? defined?(@routes) end def has_migrations? paths["db/migrate"].existent.any? end def find_root_with_flag(flag, default=nil) root_path = self.class.called_from while root_path && File.directory?(root_path) && !File.exist?("#{root_path}/#{flag}") parent = File.dirname(root_path) root_path = parent != root_path && parent end root = File.exist?("#{root_path}/#{flag}") ? root_path : default raise "Could not find root path for #{self}" unless root RbConfig::CONFIG['host_os'] =~ /mswin|mingw/ ? Pathname.new(root).expand_path : Pathname.new(root).realpath end def default_middleware_stack ActionDispatch::MiddlewareStack.new end def _all_autoload_once_paths config.autoload_once_paths end def _all_autoload_paths @_all_autoload_paths ||= (config.autoload_paths + config.eager_load_paths + config.autoload_once_paths).uniq end def _all_load_paths @_all_load_paths ||= (config.paths.load_paths + _all_autoload_paths).uniq end end end