插件扩展-优快云博客

本文介绍了在Ruby on Rails中通过不同方法实现插件扩展的具体代码示例，包括使用included、class_eval和extended钩子来为基类添加类方法和实例方法。

在ruby on rails3 的guides，插件扩展中有这样一段代码

http://guides.rubyonrails.org/plugins.html#add-an-instance-method

module Yaffle
  def self.included(base)
    base.send :extend, ClassMethods
  end
 
  module ClassMethods
    def acts_as_yaffle(options = {})
      cattr_accessor :yaffle_text_field
      self.yaffle_text_field = (options[:yaffle_text_field] || :last_squawk).to_s
      send :include, InstanceMethods
    end
  end
 
  module InstanceMethods
    def squawk(string)
      write_attribute(self.class.yaffle_text_field, string.to_squawk)
    end
  end
end
 
ActiveRecord::Base.send :include, Yaffle

还可以有几种写法：

A：

module Yaffle
  def self.included(base)
    base.send :extend, ClassMethods  
    base.send :include, InstanceMethods
  end
 
  module ClassMethods
    def acts_as_yaffle(options = {})
      cattr_accessor :yaffle_text_field
      self.yaffle_text_field = (options[:yaffle_text_field] || :last_squawk).to_s
    end
  end
  
  module InstanceMethods
    def squawk(string)
      write_attribute(self.class.yaffle_text_field, string.to_squawk)
    end
  end
end

ActiveRecord::Base.send :include, Yaffle

B：

module Yaffle
  def self.included(base)
    base.send :extend, ClassMethods  

    base.class_eval do
      include InstanceMethods
    end
 end
 
  module ClassMethods
    def acts_as_yaffle(options = {})
      cattr_accessor :yaffle_text_field
      self.yaffle_text_field = (options[:yaffle_text_field] || :last_squawk).to_s
    end
  end
  
  module InstanceMethods
    def squawk(string)
      write_attribute(self.class.yaffle_text_field, string.to_squawk)
    end
  end
end

ActiveRecord::Base.send :include, Yaffle

C：

module Yaffle
  def self.included(base)
    base.send :extend, ClassMethods      
  end
 
  module ClassMethods
    def self.extended(base)
      base.send :include, InstanceMethods
    end
    def acts_as_yaffle(options = {})
      cattr_accessor :yaffle_text_field
      self.yaffle_text_field = (options[:yaffle_text_field] || :last_squawk).to_s
    end
  end
  
  module InstanceMethods
    def squawk(string)
      write_attribute(self.class.yaffle_text_field, string.to_squawk)
    end
  end
end

ActiveRecord::Base.send :include, Yaffle

［1］http://vincent253.iteye.com/blog/135213