如何使用 ActiveSupport::Concern

在使用es-model的时候, include Elasticsearch::Model, model 就有了search方法, 代码如下:

/models/article.rb

class Article < ActiveRecord::Base
  include Elasticsearch::Model
end

Article.search # is worked

如何通过ActiveSupport::Concern, 实现类似的功能呢?

test.rb

require 'active_support'

module Foo
  extend ActiveSupport::Concern

  def instance_method
    puts "this is a instance_method"
  end

  included do
   ## 定义类方法
    def self.class_method
      puts "this is a class_method"
    end
  end
end

class Test
  include Foo
end

Test.new.instance_method
Test.class_method

campo有相似代码

module Likeable
  extend ActiveSupport::Concern

  included do
    has_many :likes, as: 'likeable', dependent: :delete_all
  end

  def liked_by?(user)
    likes.where(user: user).exists?
  end
end

这样的好处是: 1. 代码复用 2. 分拆代码, 使结构更清晰.

AS::Concern的另一个作用: 解决modules之间的dependencies, 可以参考 ihower的文章.