Except For

rails plugin是什么,自己google吧
生成plugin骨架代码:

ruby script\generate plugin MyPlugin

功能需求:
在BlogController中把所有符合条件的Post(Model)生成为xml
如果不使用插件,很easy :
in BlogController

def export_to_xml
  posts = Post.find(:all, :order => 'published_date',
      :conditions => ['title = ?', 'love'])
  send_data posts.to_xml, :type => 'text/xml; charset=UTF-8;',
      :disposition => "attachment; filename=posts.xml"
end

如果使用插件,我们要求能这样:

class BlogController < ApplicationController
  my_plugin :post
  
  def to_xml
    export_to_xml
  end
end

OK,立刻满足以上的要求,进入你的project:
生成plugin

ruby script\generate plugin MyPlugin

and than to find:
vendor/plugins/my_plugin/lib/my_plugin.rb
接着就是edit了:

module MyPlugin
  
  def self.included(base)
    base.extend(ClassMethods)
  end

  class Config
    attr_reader :model
    attr_reader :model_id
    
    def initialize(model_id)
      @model_id = model_id
      @model = model_id.to_s.camelize.constantize
    end
    
    def model_name
      @model_id.to_s
    end
  end
  
  module ClassMethods
    
    def my_plugin(model_id = nil)
      model_id = self.to_s.split('::').last.sub(/Controller$/, '').pluralize.singularize.underscore unless model_id
      @my_plugin_config = MyPlugin::Config.new(model_id)
      include MyPlugin::InstanceMethods
    end
    
    def my_plugin_config
      @my_plugin_config || self.superclass.instance_variable_get('@my_plugin_config')
    end
    
  end

  module InstanceMethods
    
    def export_to_xml
      data = self.class.my_plugin_config.model.find(:all, :order => 'published_date', :conditions => conditions_for_collection)
      send_data data.to_xml, :type => 'text/xml; charset=UTF-8;',
        :disposition => "attachment; filename=#{self.class.my_plugin_config.model_name.pluralize}.xml"
    end
    
    # 在controller中覆盖此method,写入满足的条件
    def conditions_for_collection
    end
    
  end

end

OK了吗? No No No 还要让rails加载plugin,在rails应用启动时,会到vendor/plugins目录查找所有plugin,并执行其中的init.rb
那么就edit init.rb

ActionController::Base.class_eval do
  include MyPlugin
end

或edit这样:

require 'my_plugin'
ActionController::Base.send :include, MyPlugin

最后就按上面的需求写入controller了