ruby-on-rails-3 – Rails HABTM自连接错误

发布时间：2020-12-17 04:18:58 所属栏目：百科来源：网络整理

导读：在我的应用程序中,用户可以关注许多用户,并且可以跟随许多用户. 我尝试使用has_and_belongs_to_many关联对此进行建模 class User ActiveRecord::Base has_and_belongs_to_many :followers,class_name: "User",foreign_key: "followee_id",join_table: "follo

在我的应用程序中,用户可以关注许多用户,并且可以跟随许多用户.
我尝试使用has_and_belongs_to_many关联对此进行建模

class User < ActiveRecord::Base
  has_and_belongs_to_many :followers,class_name: "User",foreign_key: "followee_id",join_table: "followees_followers"
  has_and_belongs_to_many :followees,foreign_key: "follower_id",join_table: "followees_followers"
end

另外,我为连接表创建了一个迁移,如下所示：

class FolloweesFollowers < ActiveRecord::Migration
  def up
    create_table 'followees_followers',:id => false do |t|
        t.column :followee_id,:integer
        t.column :follower_id,:integer
    end
  end

  def down
    drop_table 'followees_followers'
  end
end

当我尝试访问用户的关注者(User.first.followers)时,它会抛出一个错误：

SQLException: no such column: followees_followers.user_id: SELECT "users".* FROM "users" INNER JOIN "followees_followers" ON "users"."id" = "followees_followers"."user_id" WHERE "followees_followers"."followee_id" = 1

我不明白为什么要访问followees_followers.user_id.我错过了什么吗？

解决方法

设置多对多自联接时,：foreign_key和 :association_foreign_key选项很有用.

class User < ActiveRecord::Base
  has_and_belongs_to_many :followers,join_table: "followees_followers",association_foreign_key: "follower_id"
  has_and_belongs_to_many :followees,association_foreign_key: "followee_id"
end

（编辑：李大同）

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