hook in generator from controller generator

* use hook instead of invoke so it's easy to configure
* hook into controller_generator and scaffold_controller_generator
  This feels more natural than invoking from the resource generator.

Decorators are closely related to controllers, views and helpers.
So they should be generated in that context.
If controller generation is disabled for say generating resources there
is no point in creating decorators.

lib/draper/railtie.rb

@@ -6,7 +6,7 @@ module ActiveModel
       app ||= Rails.application # Rails 3.0.x does not yield `app`
 
       Rails::Generators.configure! app.config.generators
-      require_relative '../generators/resource_override'
+      require_relative '../generators/controller_override'
     end
   end
 end

lib/generators/controller_override.rb

@@ -0,0 +1,17 @@
+require "rails/generators"
+require "rails/generators/rails/controller/controller_generator"
+require "rails/generators/rails/scaffold_controller/scaffold_controller_generator"
+
+module Rails
+  module Generators
+
+    class ControllerGenerator
+      hook_for :decorator, default: true
+    end
+
+    class ScaffoldControllerGenerator
+      hook_for :decorator, default: true
+    end
+
+  end
+end

lib/generators/resource_override.rb

@@ -1,12 +0,0 @@
-require "rails/generators"
-require "rails/generators/rails/resource/resource_generator"
-
-module Rails
-  module Generators
-    ResourceGenerator.class_eval do
-      def add_decorator
-        invoke "decorator"
-      end
-    end
-  end
-end

spec/generators/decorator/decorator_generator_spec.rb

@@ -1,7 +1,7 @@
 require 'spec_helper'
 require 'rails'
 require 'ammeter/init'
-require 'generators/decorator/decorator_generator'
+require 'generators/rails/decorator_generator'
 
 describe Rails::Generators::DecoratorGenerator do
   destination File.expand_path("../tmp", __FILE__)