ruby-on-rails - follower_id 的 rails 作用域(has_many through source)

Question

Heroku 控制台

u = User.find(1)
u.followers.count 

(1.4ms) SELECT COUNT(*) FROM "users" INNER JOIN "relationships" ON "users"."id" = "relationships"."follower_id" WHERE "relationships"."followed_id" = $1 [["followed_id", 1]]

=> 1

relationship.rb

class Relationship < ActiveRecord::Base
  belongs_to :follower, class_name: "User"
  belongs_to :followed, class_name: "User"
  validates :follower_id, presence: true
  validates :followed_id, presence: true
end

用户.rb

has_many :active_relationships, class_name:  "Relationship",
                                foreign_key: "follower_id",
                                dependent:   :destroy
has_many :passive_relationships, class_name:  "Relationship",
                                foreign_key: "followed_id",
                                dependent:   :destroy
has_many :following, through: :active_relationships, source: :followed
has_many :followers, through: :passive_relationships, source: :follower

我想创建一个范围，按用户的关注者数量对用户进行排序

Answer 1

使用以下查询，它会根据关注者的升序为您提供用户。如果您希望 User 位于顶部且关注者最多，则可以将 asc 替换为 desc。

User.joins(:followers).group('users.id').order('count(*) asc')

更新:

如果你想在 User 模型中使用 Scope。

scope :by_followers_count, -> { joins(:followers).group('users.id').order('count(*) asc') }