如何在gem中扩展ApplicationController？

Question

我想我会想出一个灵活的方法来扩展Rails 3.x gem中的ApplicationController.

在我的宝石中lib/my_namespace/my_controller.rb,我有:

class MyNamespace::MyController < ApplicationController

  before_filter :some_method
  after_filter :another_method

  def initialize
    # getting classname of the subclass to use for lookup of the associated model, etc.
    # and storing the model_class in an instance variable
    # ...
  end

  # define :some_method, :another_method, etc.
  # ...

private
  attr_accessor :subclass_defined_during_initialize # etc.

  # etc.
end

但是当加载Gem时,app/controllers/application_controller.rb尚未加载,因此失败:

/path/to/rvm/gemset/gems/activesupport-3.2.6/lib/active_support/dependencies.rb:251:
in `require': cannot load such file -- my_gem_name/application_controller (LoadError)

作为一种解决方法,我在我的gem中定义了ApplicationController lib/gem_namespace/application_controller.rb:

class ApplicationController < ActionController::Base
end

我假设即使我在那里定义它,它也会在我的Rails 3应用程序中重新定义app/controllers/application_controller.rb,这样扩展的应用程序中的两个控制器ApplicationController和扩展的控制器MyNamespace::MyController将直接或间接扩展定义的ApplicationController app/controllers/application_controller.rb.

但是,我们注意到在加载gem之后,扩展的控制器ApplicationController无法访问定义的方法app/controllers/application_controller.rb.此外,该ApplicationHelper (app/helpers/application_helper.rb)模块不再被其他辅助模块加载.

我如何ApplicationController在gem中的控制器中进行扩展,以便定义a before_filter和after_filterto并使用initialize访问类的名称来确定它可以在其方法中存储和使用的关联模型的类？

2012/10/22更新:

这是我想出的:

在lib/your_gem_name/railtie.rb:

module YourGemsModuleName
  class Railtie < Rails::Railtie
    initializer "your_gem_name.action_controller" do
    ActiveSupport.on_load(:action_controller) do
      puts "Extending #{self} with YourGemsModuleName::Controller"
      # ActionController::Base gets a method that allows controllers to include the new behavior
      include YourGemsModuleName::Controller # ActiveSupport::Concern
    end
  end
end

并在lib/your_gem_name/controller.rb:

module YourGemsModuleName
  module Controller
    extend ActiveSupport::Concern

    # note: don't specify included or ClassMethods if unused

    included do
      # anything you would want to do in every controller, for example: add a class attribute
      class_attribute :class_attribute_available_on_every_controller, instance_writer: false
    end

    module ClassMethods
      # notice: no self.method_name here, because this is being extended because ActiveSupport::Concern was extended
      def make_this_controller_fantastic
        before_filter :some_instance_method_available_on_every_controller # to be available on every controller
        after_filter :another_instance_method_available_on_every_controller # to be available on every controller
        include FantasticStuff
      end
    end

    # instance methods to go on every controller go here
    def some_instance_method_available_on_every_controller
      puts "a method available on every controller!"
    end

    def another_instance_method_available_on_every_controller
      puts "another method available on every controller!"
    end

    module FantasticStuff
      extend ActiveSupport::Concern

      # note: don't specify included or ClassMethods if unused

      included do
        class_attribute :class_attribute_only_available_on_fantastic_controllers, instance_writer: false
      end

      module ClassMethods
        # class methods available only if make_this_controller_fantastic is specified in the controller
        def some_fanastic_class_method
          put "a fantastic class method!"
        end
      end

      # instance methods available only if make_this_controller_fantastic is specified in the controller
      def some_fantastic_instance_method
        puts "a fantastic instance method!"
      end

      def another_fantastic_instance_method
        puts "another fantastic instance method!"
      end
    end
  end
end

Answer 1

对于这种特定类型的功能,我建议在gem中创建一个模块,并在Application Controller中包含该模块

class ApplicationController < ActionController::Base
  include MyCoolModule
end

要在过滤器之前添加等(将其添加到您的模块)

def self.included(base)
  base.send(:before_filter, my_method)
end

更新:你可以做到base.before_filter :my_method更清洁.

Answer 2

这是一个Gist ,它展示了如何访问子类的类并将其存储在实例变量中,并在前后过滤器中访问它.它使用include方法.