require 'rails/railtie' require 'active_support/core_ext/module/delegation' require 'pathname' require 'rbconfig' require 'rails/engine/railties' module Rails # Rails::Engine allows you to wrap a specific Rails application and share it across # different applications. Since Rails 3.0, every Rails::Application is nothing # more than an engine, allowing you to share it very easily. # # Any Rails::Engine is also a Rails::Railtie, so the same methods # (like rake_tasks and +generators+) and configuration available in the # latter can also be used in the former. # # == 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 config/application.rb # (or in your +Gemfile+) and it will automatically load models, controllers and helpers # inside +app+, load routes at config/routes.rb, load locales at # config/locales/*, and load tasks at lib/tasks/*. # # == Configuration # # Besides the +Railtie+ configuration which is shared across the application, in a # Rails::Engine you can access autoload_paths, eager_load_paths # and autoload_once_paths, which, differently from a Railtie, 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 config.generators 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 config.app_generators: # # 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, both your application and engines do not have hardcoded paths. # This means that you are not required to place your controllers at app/controllers, # but in any place which you find convenient. # # For example, let's suppose you want to place your controllers in lib/controllers. # All you would need to do is: # # class MyEngine < Rails::Engine # paths["app/controllers"] = "lib/controllers" # end # # You can also have your controllers loaded from both app/controllers and # lib/controllers: # # 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 # # Your Application class adds a couple more paths to this set. And as in your # Application,all folders under +app+ are automatically added to the load path. # So if you have app/observers, it's 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 rack endpoint, it can also have a middleware stack. The usage is exactly # the same as in Application: # # 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 /blog, and /blog/omg points to application's # controller. In such a situation, requests to /blog/omg will go through +MyEngine+, # and if there is no such route in +Engine+'s routes, it will be dispatched to main#omg. # 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 mount(MyEngine::Engine => '/my_engine'), # it's used as default :as option # * some of the rake tasks are based on engine name, e.g. my_engine:install:migrations, # my_engine:install:assets # # Engine name is set by default based on class name. For MyEngine::Engine it will be # my_engine_engine. You can change it manually it manually using the engine_name 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 they were created inside the application. This means all application helpers and named routes # will be available to your engine's controllers. # # 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 # url_helpers from MyEngine::Engine.routes. # # The next thing that changes in isolated engines is the behaviour 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 MyEngine::ApplicationContoller. Furthermore, you don't # need to use longer url helpers like my_engine_articles_path. Instead, you should simply use # articles_path as you would do with your application. # # To make that behaviour consistent with other parts of the framework, an isolated engine also has influence on # ActiveModel::Naming. When you use a namespaced model, like MyEngine::Article, 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 #=> # end # # Additionally isolated engine will set its name according to namespace, so # MyEngine::Engine.engine_name #=> "my_engine". It will also set MyEngine.table_name_prefix # to "my_engine_", changing MyEngine::Article model to use my_engine_article 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 # url_helpers 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: # # # APP/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 my_engine helper inside your application: # # class FooController < ApplicationController # def index # my_engine.root_url #=> /my_engine/ # end # end # # There is also a main_app 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 :as option given to mount takes the engine_name 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 polymorphic_url, 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 my_engine.user_path(@user) to generate the proper route. # # == Migrations & seed data # # Engines can have their own migrations. The default path for migrations is exactly the same # as in application: db/migrate # # 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 application and rerun copying migrations. # # If your engine has migrations, you may also want to prepare data for the database in # the seeds.rb file. You can load that data using the load_seed method, e.g. # # MyEngine::Engine.load_seed # class Engine < Railtie autoload :Configuration, "rails/engine/configuration" autoload :Railties, "rails/engine/railties" 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 = 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) name = engine_name _railtie = self mod.singleton_class.instance_eval do define_method(:_railtie) do _railtie end unless mod.respond_to?(:table_name_prefix) define_method(:table_name_prefix) do "#{name}_" end 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 super paths["lib/tasks"].existent.sort.each { |ext| load(ext) } end def 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 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 initializers initializers = [] railties.all { |r| initializers += r.initializers } initializers += super 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 File.exist?(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 do environment = paths["config/environments"].existent.first require environment if environment end initializer :append_assets_path do |app| app.config.assets.paths.unshift *paths["vendor/assets"].existent app.config.assets.paths.unshift *paths["app/assets"].existent 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 routes? defined?(@routes) end def has_migrations? paths["db/migrate"].first.present? 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