使用包含同名类方法的模块扩展类

Question

我通过here 和here 描述的显着模式扩展了我的ActiveRecord 类。 我找不到安全的方法让我的新包含的类方法（extend_with_mod_a 和 extend_with_mod_b）调用它们自己的类方法（bar）

require 'active_record'

module ModA
  extend ActiveSupport::Concern

  module ClassMethods

    def extend_with_mod_a
      puts "extending #{self} with ModA"
      bar
    end

    def bar
      puts "this is method bar of ModA"
    end

  end

end


module ModB
  extend ActiveSupport::Concern

  module ClassMethods

    def extend_with_mod_b
      puts "extending #{self} with ModB"
      bar
    end

    def bar
      puts "this is method bar of ModB"
    end

  end

end

ActiveRecord::Base.send :include, ModA
ActiveRecord::Base.send :include, ModB

class TestModel < ActiveRecord::Base

  extend_with_mod_a
  extend_with_mod_b

end

输出是

extending with ModA
this is method bar of ModB
extending with ModB
this is method bar of ModB

当然，调用哪个 bar 方法取决于 ActiveRecord 包含调用顺序。我想在extend_with_mod_a 方法定义中使用类似ModA::ClassMethods.bar 的东西

Answer 1

module ModA
  extend ActiveSupport::Concern

  module ClassMethods
    def bar
      puts "this is method bar of ModA"
    end

    # grab UnboundMethod of ModA::ClassMethods::bar
    a_bar = instance_method(:bar)

    # using define_method to capture a_bar
    define_method :extend_with_mod_a do
      puts "extending #{self} with ModA"
      # invoke ModA::ClassMethods::bar properly bound to the class being extended/included with ModA
      a_bar.bind(self).call
    end
  end
end

Answer 2

尝试:prepend你的模块。

ActiveRecord::Base.send :prepend, ExtModule