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

user.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，通过followers.count订购用户

Answer 1

使用以下查询，它为用户提供基于其关注者的升序。如果您希望asc位于最高关注者的顶部，则可以将desc替换为User。

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

更新：

如果要在用户模型中使用范围。

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

follower_id的rails scope（has_many through source）

1 个答案: