![]() In such a situation you must decide whether to leave that migration or rename the migration in the application and rerun copying migrations. Note that some of the migrations may be skipped if a migration with the same name already exists in application. To use engine's migrations in application you can use the rake task below, which copies them to application's dir: rake ENGINE_NAME:install:migrations ![]() The default path for migrations is exactly the same as in application: db/migrate Migrations & seed dataĮngines can have their own migrations. Take into account 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. It will include all of the helpers from engine's directory. If you want to include all of the engine's helpers, you can use the helper method on an engine's instance: class ApplicationController < ActionController::Base If you want to share just a few specific helpers you can add them to application's helpers in ApplicationController: class ApplicationController < ActionController::Base Sometimes you may want to isolate engine, but use helpers that are defined for it. All you need to do is pass the helper as the first element in array with attributes for URL: form_for([my_engine, code will use to generate the proper route. Let's say that you want to create a form pointing to one of the engine's routes. Note that the :as option given to mount takes the engine_name as default, so most of the time you can simply omit it.įinally, if you want to generate a URL to an engine's route using polymorphic_url, you also need to pass the engine helper. There is also a main_app helper that gives you access to application's routes inside Engine: module MyEngine Now, you can use the my_engine helper inside your application: class FooController /my_engine/ Mount MyEngine::Engine => "/my_engine", as: "my_engine" Consider such a scenario: # config/routes.rb When you mount an engine in an application's routes, a special helper is created to allow you to do that. Since you can now mount an engine inside application's routes, you do not have direct access to Engine's url_helpers inside Application. It will also set MyEngine.table_name_prefix to “my_engine_”, meaning for example that MyEngine::Article will use the my_engine_articles database table by default. You can change it manually using the engine_name method: module MyEngineĬlass Engine "articles_path" # not "my_engine_articles_path"Īdditionally, an isolated engine will set its own name according to its namespace, so MyEngine::Engine.engine_name will return “my_engine”. For MyEngine::Engine it will be my_engine_engine. Rake task for installing migrations my_engine:install:migrationsĮngine name is set by default based on class name. Routes: when you mount an Engine with mount(MyEngine::Engine => '/my_engine'), it's used as default :as option There are some places where an Engine's name is used: Now, Engine will get only requests that were not handled by Application. 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. MyEngine is mounted at /blog, and /blog/omg points to application's controller. Note that now there can be more than one router in your application, and it's better to avoid passing requests through many routers. The usage is exactly the same as in Application: module MyEngine To do that, use the endpoint method: module MyEngineĪs an engine can now be a Rack endpoint, it can also have a middleware stack. It can be useful if you have a Rack application that you would like to provide with some of the Engine's features. EndpointĪn engine can also be a Rack application. If you have an app/services folder for example, it will be added by default. And as in your Application, all folders under app are automatically added to the load path. The Application class adds a couple more paths to this set. If you want a gem to 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 Every Rails::Application is just an engine, which allows for simple feature and application sharing.Īny Rails::Engine is also a Rails::Railtie, so the same methods (like rake_tasks and generators) and configuration options that are available in railties can also be used in engines. Rails::Engine allows you to wrap a specific Rails application or subset of functionality and share it with other applications or within a larger packaged application.
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