Data Service Ruby Core

base.rb

module DataService
  RELATION_ID = 'relation'

  module DataApi
    def self.included base
      base.singleton_class.send :attr_accessor, # private method
        :json_attributes,                       # 数据模型的json属性定义
        :expire_time,                           # 数据模型的过期时间
        :model_class,                           # 数据模型对应的Activerecord, 默认值是根据类名推断, 可以在这里覆盖
        :cache_key                              # 缓存的key, 有默认值, 通常不需要设置
    end

    # json_attributes 的组装过程
    def attrs_map
      klass.json_attributes.inject({}) do |target, attr|
        target[attr] = respond_to?(attr) ? send(attr) : model.send(attr)
        target
      end
    end

    def klass
      is_a?(Class) ? self.singleton_class : self.class
    end

    def cache_key_with_namespace
      "data_service:#{klass.cache_key}:#{id}"
    end

    def save
      return nil unless model # 如果找不到AD对象
      json_string = attrs_map.to_json
      Redis.deal_service.setex(cache_key_with_namespace, klass.expire_time, json_string)
      json_string
    end

    def delete
      Redis.deal_service.del(cache_key_with_namespace)
    end

    def relation?
      id == RELATION_ID
    end

  end

  class Base
    attr_accessor :model, :id

    # Base#new通常只会在实例型数据上使用
    def initialize id
      self.id = id
      self.model = self.class.model_class.find_by_id id #找到实例型数据对应的AD对象
    end

    class << self
      def inherited subclass
        subclass.include DataApi
        subclass.singleton_class.include DataApi

        # model_class的默认值
        name = subclass.name.demodulize
        top_model = Object.const_get(name)
        name_key = name.downcase

        # 设置实例型数据模型的model_class和cache_key
        subclass.model_class = top_model
        subclass.cache_key = name_key

        # 设置关系型数据模型的model_class和cache_key
        subclass.singleton_class.model_class = top_model
        subclass.singleton_class.cache_key = name_key

        # 关系型数据模型的id是固定的字符串relation
        subclass.send(:define_singleton_method, :id) { RELATION_ID }
        subclass.send(:define_singleton_method, :model) { top_model }
      end
    end
  end

end