问在mysql中存储JSON数据

EN

module MultiAttr

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

  module ClassMethods
    def multi_attr(*args)
      args.each do |attr_name|
        class_eval <<-EOF
          has_many attr_#{attr_name}, :class_name => "MultiAttributes", :as => :owner,
             :conditions => {:key => '#{attr_name.singularize}'}

          def add_#{attr_name.singularize}(val)
            self.attr_#{attr_name}.create(:key => #{attr_name.singularize}, :value => val)
            #{attr_name}
          end

          def #{attr_name}
            self.attr_#{attr_name}.map(&:to_attr_model)
          end

        EOF
      end
    end

  end


end

class AttrModel < String

  def initialize(record)
    @record = record
    super(record.value)
  end

  def remove
    @record.destroy
  end

end


#owner_type, owner_id, key, value
class MultiAttribute < ActiveRecord::Base
  belongs_to :owner, :polymorphic => true

  def to_attr_model
    @attr_model ||= AttrModel.new(self)
  end
end

class User < ActiveRecord::Base
  include MultiAttr
  multi_attr :emails, :addresses
end

user.emails #=> ["abc@example.com"]
user.add_email "qq@example.com" #=> 
user.emails.first.remove