Mongoid的counter_cache

引用

lib/mongoid/counter_cache.rb

# encoding: utf-8
module Mongoid #:nodoc:

	# This module handles the behaviour for Counter Cache.
	module CounterCache #:nodoc:
	  extend ActiveSupport::Concern
	  included do
	  	set_callback :create, :after, :increment_counter
	  	set_callback :destroy, :after, :decrement_counter
	  	unless methods.include? 'counter_cache'
	  	  class_attribute :counter_cache
	  	  self.counter_cache = true
	  	end
	  end

	  # used by increment_counter and decrement_counter
	  def update_counter(count)
	    if count.is_a?(Integer)
  	    associations = reflect_on_all_associations(:referenced_in)
  	    for association in associations
  	      parent_class = association.class_name.constantize
  	      counter_name = "#{association.inverse_of}_count"
  	      object_id = self["#{association.name}_id".to_sym]
  	      if !object_id.nil? && parent_class.fields.keys.include?(counter_name)
  	        parent_class.find(object_id).inc(counter_name.to_sym, count)
  	      end
  	    end
	    end
	  end
	  
	  # Increment a number field by one, usually representing a count.
	  # This is only called on create.
	  #
	  # @example Increment a number field by one.
	  #   post.increment_counter
	  def increment_counter
	    update_counter(1)
	  end
	  
	  # Decrement a number field by one, usually representing a count.
	  # This is only called on destroy.
	  #
	  # @example Decrement a number field by one.
	  #   post.decrement_counter
	  def decrement_counter
	  	update_counter(-1)
	  end
	end
end

引用

app/models/blog.rb

require 'rtranslate' # 谷歌翻譯
require 'mongoid/counter_cache'
class Blog
  include Mongoid::Document
  include Mongoid::Timestamps
  include Mongoid::CounterCache
  # 數據關聯
  referenced_in :owner, # 擁有者
    :class_name => 'Person', :inverse_of => :blogs
  references_many :posts # 帖子
  # 數據效驗
  validates :title, :presence => true
  validates :permalink,
    :uniqueness => true, 
    :length => { :minimum => 4 },
    :allow_blank => true,
    :format => { :with => /^[a-zA-Z0-9\_\-\ ]*?$/i }
  #　數據字段
  field :title, :null => false
  field :permalink, :null => false
  field :tagline
  field :owner_name
  field :owner_avatar
  #　計數器
  field :posts_count, :type => Integer, :default => 0 # 帖子數
  # 主鍵
  key :permalink
  # 索引
  index :permalink, :unique => true
  # 作用域：
  default_scope desc(:updated_at) # 默認
  # 回調：
  before_validation :generate_permalink

  # 所有者信息
  def owner=(person)
    self.owner_id = person.id
    self.owner_name = person.display_name
    self.owner_avatar = person.avatar!
  end
  
  protected
  
  def generate_permalink # 翻譯成英文
    self.permalink = Translate.t(title, 'UNKNOWN', 'English') if permalink.blank?
  end
end

评论

1 楼 mimosa 2011-06-07  

你太悲劇啦
應該這樣有木有