Rails engines and namespacing. Cases where namespaces are required?

Question

I'm a bit confused with namespacing in engines. In a Rails engine, where isolate_namespace is used,

module Blog
  class Engine < Rails::Engine
    isolate_namespace Blorgh
  end
end

when is it required that you refer to objects with the namespace Blog (e.g. Blog::Post vs just Post)?

As for example, within the controller of a Post resource of the engine, is it ok to just do Post.find? When it is absolutely required that you use Blog::Post?

Also in models associations, assume that Post has_many :comments. Somehow, I was expecting to define it as follows:

class Post < ActiveRecord::Base
  :has_many "blog/comments"
end

since everything is namespaced (models, table names, ...), but it looks like has_many :comments just works. Why namespacing is not used in association keys, and in the case where a Comment resource exists in the host applications, how does rails know which Comment I'm referring to?

score 2 · Accepted Answer · answered Aug 30 '12 at 12:23

When you're inside some module, you can refer to other member of the module without giving the module name, eg:

module Foo

  class Bar
    def initialize
      @baz = Baz.new # same as Foo::Baz.new
    end
  end
  class Baz

  end
end

If Baz doesn't exist in the current module, it will cascade down to find the definition, eventually calling const_missing (upon which is built the autoload of classes in Rails), then throw an error if nothing is found.

Rest of your questions is answered here.

Rails engines and namespacing. Cases where namespaces are required?

1 Answers1