Rails 3.1 Engines: Full vs. Mountable

Hi all,

I was hoping someone could please clarify the differences between a
full engine and a mountable one.

I have noticed the following:

** Full Engine **
- With a full engine, the parent application inherits the routes from
the engine. It is not necessary to specify anything in parent_app/
config/routes.rb. Specifying the gem in Gemfile is enough. The
engine routes are specified as:

# my_engine/config/routes.rb
Rails.application.routes.draw do
# whatever

- No namespacing of models, controllers, etc. These are immediately
accessible to the parent application.

** Mountable Engine **
- The engine's namespace is isolated by default.

# my_engine/lib/my_engine/engine.rb
module MyEngine
  class Engine < Rails::Engine
    isolate_namespace MyEngine

- With a mountable engine, the routes are namespaced and the parent
app can bundle this functionality under a single route:

# my_engine/config/routes.rb
MyEngine::Engine.routes.draw do

# parent_app/config/routes.rb
Rails.application.routes.draw do
  mount MyEngine::Engine => "/engine", :as => "namespaced"

- Models, controllers, etc are isolated from the parent application -
although helpers can be shared easily.

Is this correct and are these the main differences? Are there any
other differences between a full and mountable engine that I missed?


I take it no one has poked around with the Rails 3.1 engines yet?


I'm interested in this, too, but I haven't used 3.1 yet. Let us know
what you find out!

Hi Paul,

Here's what I have found so far:


I'll post Part 2 later tonight. Hope that helps you out.