Question

我有以下代码（有点简化......

create_table :signatures do |t|
  t.integer :signer_id
  t.integer :card_id

  t.timestamps
end

模型看起来像......

class Signature < ActiveRecord::Base
    belongs_to :card
    belongs_to :user
end

class Card < ActiveRecord::Base
    has_many :signatures
    has_many :signers, :through => :signatures, :foreign_key => "card_id"
end


class User < ActiveRecord::Base

    has_many :sent_cards, :class_name => "Card", :foreign_key => "sender_id"
    has_many :received_cards, :class_name => "Card", :foreign_key => "recipient_id"

    has_many :signatures
    has_many :signed_cards, :through => :signatures, :foreign_key => "signer_id"

end

我使用rails控制台看到以下错误......

ruby-1.9.2-p0 > u15.signed_cards
ActiveRecord::HasManyThroughSourceAssociationNotFoundError: Could not find the source association(s) :signed_card or :signed_cards in model Signature. Try 'has_many :signed_cards, :through => :signatures, :source => <name>'. Is it one of :card or :user?
    from /home/slabounty/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.1.0/lib/active_record/reflection.rb:517:in `check_validity!'
    from /home/slabounty/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.1.0/lib/active_record/associations/association.rb:27:in `initialize'
    from /home/slabounty/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.1.0/lib/active_record/associations/collection_association.rb:24:in `initialize'
    from /home/slabounty/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.1.0/lib/active_record/associations.rb:164:in `new'
    from /home/slabounty/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.1.0/lib/active_record/associations.rb:164:in `association'
    from /home/slabounty/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.1.0/lib/active_record/associations/builder/association.rb:41:in `block in define_readers'
    from (irb):11
    from /home/slabounty/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.1.0/lib/rails/commands/console.rb:45:in `start'
    from /home/slabounty/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.1.0/lib/rails/commands/console.rb:8:in `start'
    from /home/slabounty/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.1.0/lib/rails/commands.rb:40:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'

当我添加source => :card/:user时，我会得到同样的信息（在这种情况下应该是卡片我相信）。

我在这里做错了什么想法？

显示部分解决方案，因为我想清理一个一些事情。迁移与以前的版本保持一致。我现在看到SQL错误（见下文），它在Signature中找不到user_id。一世讨厌说出来，但大多数情况下我一直在投入：foreign_key，我认为他们可能无济于事。

    class Signature < ActiveRecord::Base
        belongs_to :card
        belongs_to :signer, :class_name => "User"
    end


    class Card < ActiveRecord::Base
        # Correct
        has_many :signatures
        has_many :signers, :through => :signatures, :source => :user

    end

    class User < ActiveRecord::Base
        # Wrong!
        has_many :signatures, :foreign_key => "signer_id"
        has_many :signed_cards, :through => :signatures, :source => :card
    end

有错误（减去堆栈跟踪）

ruby-1.9.2-p0 >   u15.signed_cards
  Card Load (0.5ms)  SELECT "cards".* FROM "cards" INNER JOIN "signatures" ON "cards"."id" = "signatures"."card_id" WHERE "signatures"."user_id" = 15 ORDER BY cards.created_at DESC
SQLite3::SQLException: no such column: signatures.user_id: SELECT "cards".* FROM "cards" INNER JOIN "signatures" ON "cards"."id" = "signatures"."card_id" WHERE "signatures"."user_id" = 15 ORDER BY cards.created_at DESC
ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column: signatures.user_id: SELECT "cards".* FROM "cards" INNER JOIN "signatures" ON "cards"."id" = "signatures"."card_id" WHERE "signatures"."user_id" = 15 ORDER BY cards.created_at DESC

Card.signers按预期返回一个空数组。

仍然在寻找这方面的帮助。我没有找到很多简单，直接的解释，你没有使用相同的名称（即你需要一个foreign_key和源。

Answer 1

用户应该像这样定义：

class User < ActiveRecord::Base

  has_many :sent_cards, :class_name => "Card", :foreign_key => "sender_id"
  has_many :received_cards, :class_name => "Card", :foreign_key => "recipient_id"

  has_many :signatures
  has_many :signed_cards, :through => :signatures, :source => :card

end

如果您的关联名称与：通过使用的名称不同，则必须定义来源参数。如果您查看异常消息，明确会要求您执行此操作。

Answer 2

好吧，既然我有这么难的时候，我想向大家展示一下最终版看起来像。我有这么难的原因很大一部分原因实现这一目标的是轨道控制台似乎没有这样的事实在我做出更改时正确地重新加载东西。直到我，我才意识到这一点一天晚上放弃了，第二天早上又回来了前一晚的工作没有，而且工作不起作用的是。

迁移是一样的，但为了完整起见，我会重复它。

def change
    create_table :signatures do |t|
        t.integer :signer_id
        t.integer :card_id
        t.boolean :signed,    :default => false
        t.text :message

        t.timestamps
    end
end

Signature类有两个belongs_to，卡就是这种情况通常在示例中显示，签名者是用户类型。

class Signature < ActiveRecord::Base
    belongs_to :card
    belongs_to :signer, :class_name => "User"
end

用户有很多签名（即使您不直接使用它们也是必需的）一个dmany signed_cards通过签名与卡的来源（告诉Rails 哪个类类型为signed_cards。

class User < ActiveRecord::Base
    has_many :signatures, :foreign_key => "signer_id"
    has_many :signed_cards, :through => :signatures, :source => :card 
end

最后，该卡有许多签名（再一次是必要的）和许多签名者通过签名和signer_id的签名者的foreign_key。

class Card < ActiveRecord::Base
    has_many :signatures
    has_many :signers, :through => :signatures, :foreign_key => 'signer_id'
end

希望这可以帮助其他人遇到类似问题。

Rails：ActiveRecord :: HasManyThroughSourceAssociationNotFoundError：找不到源关联

2 个答案: