Rails4:如何在使用accepts_nested_attributes_for时触发attr_accessor的回调

Question

请检查伪代码:

class Team
  has_many :users
  accepts_nested_attributes_for :users, allow_destroy: true
end

class User
  belongs_to :team
  has_many :addresses
  accepts_nested_attributes_for :addresses
  attr_accessor :dummy

  before_validation :generate_addresses_attributes
  def generate_addresses_attributes
    # Use the dummy value to set the addresses_attributes
  end
end

现在执行时team.update(users_attributes: [{"0" => { dummy: "changed!" }}])(其他字段除了dummy属性不会改变),它不会触发#generate_addresses_attributes回调,因为它认为没有任何改变,没有保存,没有回调......

所以我的问题是如何触发虚拟属性的回调,或者强制save为accept_nested_attributes_for.

谢谢!

Answer 1

最后,我找到了两个解决方案:

1. 在Team模型中添加回调以手动触发回调功能

2. 使用attribute_will_change!覆盖setter方法:

   class User
     belongs_to :team
     has_many :addresses
     accepts_nested_attributes_for :addresses
     attr_accessor :dummy
   
     def dummy=(value)
       attribute_will_change!("dummy") if @dummy != value
       @dummy = value
     end
   
     ...
   end
   

Answer 2

我发现 Rails 5.1+attribute比attr_accessor这个用例效果更好。

attribute 弄脏对象，从而在保存时触发回调。

class User
  belongs_to :team
  has_many :addresses
  accepts_nested_attributes_for :addresses
  attribute :dummy, :string

  before_validation :generate_addresses_attributes
  def generate_addresses_attributes
    # Use the dummy value to set the addresses_attributes
  end
end