Question

我在这样的关系中有一个共同的模型：

user.rb

class User < ApplicationRecord
  has_many :likes

diary.rb

class Diary < ApplicationRecord
  has_many :likes
  has_many :liked_users, through: :likes, source: :user

like.rb

class Like < ApplicationRecord
  belongs_to :user
  belongs_to :diary

现在，我想订购

@diary.liked_users

来自likes.created_at。

哪种方法最简单，性能最快？

Answer 1

简短答案

@diary.liked_users.order('likes.created_at ASC')

为什么行得通？

因此内部rails发出如下查询：

Select users.* FROM like INNER JOIN users ON users.id = like.user_id WHERE like.diary_id = 1

1仅是您要应用此方法的日记ID的示例。

这意味着查询中已经存在likes表

因此，@diary.liked_users.order('likes.created_at ASC')会生成如下内容：

Select users.* FROM likes INNER JOIN users ON users.id = likes.user_id WHERE likes.diary_id = 1 ORDER BY likes.created_at ASC