Rails使用特定字段的錯誤ID創建對象

Question

我正在開發類似於twitter中的提及系統。所以我在處理這個問題中的三個類：Post，User和Mention。提及對象具有一個mentioned_id字段（提到的用戶）和一個post_id（它發生的帖子）。 我在編寫測試時發現了一些奇怪的問題，所以我打開了一個控制檯會話，這是發生了什麼事情： 我創建了兩個用戶，兩個帖子和兩個提及。如果您發現，當我創建了第二個提及（@ mention2）@mentioned_id的ID不正確的用戶ID：

ruby-1.9.2-p180 :001 > @user1 = Factory(:user, :email => Factory.next(:email)) 

=> #<User id: 1, name: "Fulano", email: "person_number1@example.com", created_at: "2011-09-11 15:38:11", updated_at: "2011-09-11 15:38:11", encrypted_password: "ede4e8cc0440b8bd9fdc059e8496154715b6592690157aac618...", salt: "4bfae8fecee1629b7c290c2d5af5bd3bbeb38c4ce76546d7176...", admin: false> 

ruby-1.9.2-p180 :002 > @user2 = Factory(:user, :email => Factory.next(:email)) 

=> #<User id: 2, name: "Fulano", email: "person_number2@example.com", created_at: "2011-09-11 15:39:06", updated_at: "2011-09-11 15:39:06", encrypted_password: "ddda10f48575f63724e1db3d3cf684f2c60380325236311e15d...", salt: "911121b8942dc57116dfd24383d96874c750bc5a21fa210288b...", admin: false> 

ruby-1.9.2-p180 :003 > @post1 = Factory(:post, :user => @user1) 

=> #<post id: 1, content: "Foo bar", user_id: 1, created_at: "2011-09-11 15:39:57", updated_at: "2011-09-11 15:39:57"> 

ruby-1.9.2-p180 :004 > @post2 = Factory(:post, :user => @user2) 

=> #<post id: 2, content: "Foo bar", user_id: 2, created_at: "2011-09-11 15:40:37", updated_at: "2011-09-11 15:40:37"> 

ruby-1.9.2-p180 :005 > @mention1 = @post2.mentions.create :mentioned_id => @user1 

=> #<Mention id: 1, post_id: 2, mentioned_id: 1, created_at: "2011-09-11 15:41:33", updated_at: "2011-09-11 15:41:33"> 

ruby-1.9.2-p180 :007 > @mention2 = @post1.mentions.create :mentioned_id => @user2 

=> #<Mention id: 2, post_id: 1, mentioned_id: 1, created_at: "2011-09-11 15:42:16", updated_at: "2011-09-11 15:42:16"> 

奇怪的是，如果我用@ user2.id，而不僅僅是@ user2的最後一行，一切工作正常：

ruby-1.9.2-p180 :008 > @mention2 = @post1.mentions.create :mentioned_id => @user2.id 


=> #<Mention id: 3, post_id: 1, mentioned_id: 2, created_at: "2011-09-11 15:45:16", updated_at: "2011-09-11 15:45:16"> 

任何人都可以請告訴我發生了什麼？我認爲導軌「魔術」在引用對象時負責獲取id。爲什麼它會與第一個用戶一起工作，而不是第二個用戶？

這是我提到的類代碼：

class Mention < ActiveRecord::Base 
    attr_accessible :mentioned_id 

    belongs_to :mentioned, :class_name => "User" 
    belongs_to :post 

    validates :mentioned, :presence => true 
    validates :post, :presence => true 

end 

這是代碼爲我的用戶類相關部分：

Class User < ActiveRecord::Base 

    … 

    has_many :posts, :dependent => :destroy 
    has_many :mentions, :dependent => :destroy, :foreign_key => 'mentioned_id' 

    … 

這也發生在我的規格測試：

@user = Factory(:user, :email => Factory.next(:email)) 
    @other_user = Factory(:user, :email => Factory.next(:email)) 

    @post1 = Factory(:post, :user => @other_user) 
    @post2 = Factory(:post, :user => @other_user) 
    @post3 = Factory(:post, :user => @user) 
    @mention1 = @post1.mentions.create :mentioned_id => @user 
    @mention2 = @post2.mentions.create :mentioned_id => @user 
    @mention3 = @post3.mentions.create :mentioned_id => @other_user.id 

如果我使用.id方法，但前兩項工作正確，最後一行只能正常工作。 ..

Answer 1

您試圖要求Rails將整數（mentioned_id）映射到對象（@user）。您正在@post1 = ...行上正確執行此操作，您將@other_user指定爲:user，而不是:user_id。你需要做同樣的你的@mention1 = ...線：

@mention1 = @post1.mentions.create :mentioned => @user 

然而，隨着你的代碼，因爲它是，這將不能工作，因爲你的attr_accessor線的干擾。

您可以擺脫完全行和:mentioned => @user部分將工作，或者你可以改變它像這樣，允許直接分配給:mentioned而非:mentioned_id（是的，他們真的是同樣的事情，但似乎Rails檢查attr_accessible並拒絕訪問更新:mentioned，然後才意識到:mentioned實際上只是:mentioned_id）。

attr_accessible :mentioned_id, :mentioned