Rails belongs_to協會（with：class_name）返回無

Question

我對Rails開發比較新，而且我有一個小的關聯問題。我想指出一個與它所鏈接的模型不同的協會。

我有以下2種型號：

class User < ActiveRecord::Base 
    has_many :events 
end 

class Event < ActiveRecord::Base 
    belongs_to :admin, :class_name => "User" # So we can call event.admin to retrieve the User who owns this Event 
end 

我建立一個用戶，如下所示：

event = event.create! :title => "New Event" 

user = User.create! :username => "thinkswan" 
user.events << event 
user.save 

當我跳進控制檯收到以下：

irb> user = User.find(1) 
irb> user.events 
=> [#<Event id: 1, title: "New Event", user_id: 1, created_at: "2011-06-09 06:41:09", updated_at: "2011-06-09 06:41:10">] 

irb> event = Event.find(1) 
irb> event.user_id 
=> 1 
irb> event.admin 
=> nil 

任何人都可以解釋爲什麼admin協會沒有返回它指向的用戶？謝謝！

Answer 1

您需要同時指定:class_name和:foreign_key，例如：

belongs_to :admin, :class_name => "User", :foreign_key => "user_id"