回调方法应用 及 引入到模块方法应用

1： http://ruby-china.org/topics/413

module YourPlugin
  module Mixin
 def xxx_attr(attr)
      attr = attr.to_s
      self.class_eval(%Q{
def #{attr}
  #...
end

def #{attr}=(value)
   #...
end
        }
      )
    end
  end
end

class Post
  include YourPlugin::Mixin
  xxx_attr :tag_list
end

2. http://quake.iteye.com/blog/448235

#plugins/your_plugin_name/lib/enum_attr.rb
module EnumAttr
  module Mixin
    def enum_attr(attr, enums)
      attr = attr.to_s
      self.class_eval(%Q{
ENUMS_#{attr.upcase} = enums
validates_inclusion_of attr, :in => enums.map{|e| e[1]}, :allow_nil => true
def #{attr}_name
  ENUMS_#{attr.upcase}.find{|option| option[1] == #{attr}}[0] unless #{attr}.nil?
end
        })
    end
  end
end

#plugins/your_plugin_name/init.rb
require 'enum_attr'
Object.send :include, EnumAttr::Mixin