如何使用模块动态地将类方法添加到Rails模型

Question

我在模型类上有这个代码来添加meta_searchgem 使用的搜索方法:

class Model

  self.def created_at_lteq_at_end_of_day(date)
     where("created_at <= ?", DateTime.strptime(date, '%d/%m/%Y').end_of_day)
  end

  search_methods :created_at_lteq_at_end_of_day
end

此代码将搜索方法添加到日期字段.现在,需要将此搜索方法添加到其他类和其他字段.为此,创建了此模块:

LIB/meta_search/extended_search_methods.rb

module MetaSearch
  module ExtendedSearchMethods
    def self.included(base)
      base.extend ClassMethods
    end


    module ClassMethods
      def add_search_by_end_of_day(field, format)

        method_name = "#{field}_lteq_end_of_day"

        define_method method_name do |date|
          where("#{field} <= ?", DateTime.strptime(date, format).end_of_day) 
        end

        search_methods method_name
      end
    end
  end
end


class Model
   include MetaSearch::ExtendedSearchMethods
   add_search_by_end_of_day :created_at, '%d/%m/%Y'
end

添加模块后,此错误开始增加:

undefined method `created_at_lteq_end_of_day' for #<ActiveRecord::Relation:0x007fcd3cdb0e28>

其他方案:

改变define_method以define_singleton_method

Answer 1

ActiveSupport提供了一种非常惯用且很酷的方式ActiveSupport::Concern:

module Whatever
    extend ActiveSupport::Concern

    module ClassMethods
        def say_hello_to(to)
            puts "Hello #{to}"
        end
    end
end

class YourModel
    include Whatever

    say_hello_to "someone"
end

请参阅API文档.虽然它与您的问题没有直接关系,但该included方法对于模型或控制器(范围,辅助方法,过滤器等)非常有用,ActiveSupport::Concern并且可以免费处理模块之间的依赖关系(无论是在自由中还是在啤酒中).

Answer 2

您需要添加一个,class << self这样您就可以在单例类中工作.

module Library
  module Methods
    def self.included(base)
      base.extend ClassMethods
    end

    module ClassMethods
      def add_foo
        class << self
          define_method "foo" do
            puts "Foo!"
          end #define_method
        end #class << self
      end #add_foo
    end #ClassMethods
  end #Methods
end #Library

class Test
  include Library::Methods

  add_foo
end

puts Test.foo