哈布特姆外键

Question

>我尝试使用habtm关系，但我需要使用uid作为外键

SELECT "friends".* FROM "friends" INNER JOIN "friendships" ON "friends"."uid" = "friendships"."uid" WHERE "friendships"."user_id" = 4
#User
has_and_belongs_to_many :friends, :class_name => "Friend", :join_table => "friendships", :association_foreign_key => "uid"
#Friend
has_and_belongs_to_many :users, :class_name => "User", :join_table => "friendships", :foreign_key => "uid"
SELECT "friends".* FROM "friends" INNER JOIN "friendships" ON "friends"."id" = "friendships"."uid" WHERE "friendships"."user_id" = 4

Answer 1

遵循 Rails 风格指南：

更喜欢has_many ：通过has_and_belongs_to_many。使用 has_many ：through 允许在连接模型上进行其他属性和验证

在您的情况下：

class Friendship < ActiveRecord::Base
  belongs_to :friend
  belongs_to :user
  # the validates are not mandatory but with it you make sure this model is always a link between a Friend and a User
  validates :user_id, :presence => true
  validates :uid, :presence => true # the Foreign Key is 'uid' instead of 'friend_id'
end
class User < ActiveRecord::Base
  has_many :friends, :through => :friendships
end
class Friend < ActiveRecord::Base
  has_many :users, :through => :friendships, :foreign_key => "uid"
end