从 has_and_belongs_to_many 关系返回的对象不正确
我有两个模型，User 和 Discussion
用户模型
has_and_belongs_to_many :subscribed_discussions, :class_name => 'Discussion', :join_table => 'discussions_subscriptions'
has_many :discussions
讨论模型
has_and_belongs_to_many :subscribed_users, :class_name => 'User', :join_table => 'discussions_subscriptions'
belongs_to :user
当我访问用户 u.subscribed_discussions[0].user_id 的讨论时，我与我直接从 Discussion 访问用户时相比，得到的 user 值完全不同。发现
system :029 > u.subscribed_discussions.first == Discussion.find(10)
=> true
system :030 > Discussion.find(10)
=> #<Discussion id: 10, title: "MBA", content: "What do you think about management education, speci...", user_id: 7, created_at: "2011-01-24 21:44:22", updated_at: "2011-01-24 21:44:22", group_id: nil, profile_id: 8>
system :031 > u.subscribed_discussions.first
=> #<Discussion id: 10, title: "MBA", content: "What do you think about management education, speci...", user_id: 1, created_at: "2011-01-24 21:44:22", updated_at: "2011-01-24 21:44:22", group_id: nil, profile_id: 8>
system :032 > u.id
=> 1
system :034 > Discussion.find(10).user_id
=> 7
u 是订阅讨论的用户id=10。当我通过 subscribed_discussions 关系访问讨论并访问其用户时，我得到的是 u，而不是该讨论的创建者。
I have two models, User and Discussion
User model
has_and_belongs_to_many :subscribed_discussions, :class_name => 'Discussion', :join_table => 'discussions_subscriptions'
has_many :discussions
Discussion model
has_and_belongs_to_many :subscribed_users, :class_name => 'User', :join_table => 'discussions_subscriptions'
belongs_to :user
When I access discussions from a user u.subscribed_discussions[0].user_id, I get a completely different value of user than when I access the user directly from Discussion.find
system :029 > u.subscribed_discussions.first == Discussion.find(10)
=> true
system :030 > Discussion.find(10)
=> #<Discussion id: 10, title: "MBA", content: "What do you think about management education, speci...", user_id: 7, created_at: "2011-01-24 21:44:22", updated_at: "2011-01-24 21:44:22", group_id: nil, profile_id: 8>
system :031 > u.subscribed_discussions.first
=> #<Discussion id: 10, title: "MBA", content: "What do you think about management education, speci...", user_id: 1, created_at: "2011-01-24 21:44:22", updated_at: "2011-01-24 21:44:22", group_id: nil, profile_id: 8>
system :032 > u.id
=> 1
system :034 > Discussion.find(10).user_id
=> 7
u is a user who has subscribed to the discussion with id=10. When I access the discussion through the subscribed_discussions relationship, and access its user, I get u back, instead of the creator of that discussion.
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评论（2）
我假设您的
Discussion模型belongs_to :user，这意味着讨论模型上的user_id字段将是该用户，它与has_and_belongs_to_many :subscribed_users关联。您可以发布您的模型和 schema.rb 吗？这将使您更容易理解您的模型正在做什么。
另外，我建议放弃 HABTM 并使用
has_many :through代替，它会给你一个更丰富的模型。I'm assuming your
Discussionmodelbelongs_to :user, which means theuser_idfield on the discussion model will be that user, it's unrelated to thehas_and_belongs_to_many :subscribed_usersassociation.Can you post your models and schema.rb? It'll make it easier to understand what your model is doing.
Also, I suggest moving away from HABTM and using
has_many :throughinstead, it'll give you a richer model.我在 IRC 上确认了这一点，如果表和连接表之一都有同名的列，那么这是 Rails 3 中 HABTM 关系中的一个错误。
I confirmed this on IRC that this is a bug in HABTM relationships in Rails 3, if one of the table and the join table both have a column of the same name.