Rails has_many：通过where子句

Question

我在Rails中构建了一个简单的Twitter应用程序。我想to choose three random users that are not followed by the current user。

这里是我的模型：

class User < ActiveRecord::Base 
    has_many :tweets, dependent: :destroy 
    has_many :followerships, class_name: 'Followership', foreign_key: 'followed_id' 
    has_many :followedships, class_name: 'Followership', foreign_key: 'follower_id' 
    has_many :followers, through: :followerships, source: :follower 
    has_many :followed, through: :followedships, source: :followed 
end 

class Followership < 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 

class Tweet < ActiveRecord::Base 
    belongs_to :user 
end 

我尝试使用下面的查询：

User.where.not(followers: current_user).order("RANDOM()").limit(3) 

但显然我得到no such column: users.follower_id错误不起作用。

它甚至可以做到没有SQL查询？

谢谢！

Answer 1

试试这个：

already_following = current_user.followed.map(&:id) 
@users = User.where.not(id: already_following).order("RANDOM()").limit(3) 

基本上我做什么，是已经得到了遵循用户的列表。然后，您检查用户表的id是否与已经遵循的用户匹配。