ruby-on-rails-3 - 代表不为我工作？

Question

我已经看到了http://rails-bestpractices.com/posts/15-the-law-of-demeter的委托，我喜欢这个，我想像下面这样自定义。

情况1 ：

    class Application < ActiveRecord::Base
      belongs_to :user
      delegate :name, :to => :user

      has_one :repair, :dependent => :destroy
      delegate :estimated_amount, :to => :repair

      has_one :dealership, :through => :booking
    end

    class User < ActiveRecord::Base
     def name
     return some value
    end
    end

我打过电话Application.first.user_name => undefined method `user_name' for #<Application:0xb186bf8>

案例2：我打过电话Application.first.repair_estimated_amount: => undefined method `'repair_estimated_amount' for #<Application:0xb186bf8>

案例3：我打过电话Application.first.dealership_name: => undefined method `' for #<Application:0xb186bf8>

有人可以建议如何将委托与 has_one 关系一起使用吗？

在此先感谢普拉萨德

Answer 1

您没有使用前缀选项，因此您应该只调用不带前缀的方法。

# model.rb
delegate :estimated_amount, :to => :repair

# somewhere else
Application.first.estimated_amount #=> works
Application.first.report_estimated_amount #=> exception!

但是，如果您传递前缀选项：

# model.rb
delegate :estimated_amount, :to => :repair, :prefix => true

# somewhere else
Application.first.estimated_amount #=> exception
Application.first.report_estimated_amount #=> works!

请参阅delegate()的文档