覆盖has_many关联获取器 [英] Overriding a has_many association getter

问题描述

用户可以拥有多辆汽车-

A user can have several cars -

• 用户：has_many：cars


• 汽车：belongs_to：user

• User: has_many :cars
• Car: belongs_to :user

每次我呼叫 @ user.cars 时，它都会以默认搜索顺序返回汽车的列表。

Every time I call @user.cars it returns the list of cars in default search order.

如果我希望关联在任意字段上排序，我可以这样做

If I wanted the association sorted on some arbitrary field, I could do

class User < ActiveRecord::Base
  has_many :cars, -> { order :num_wheels }
end

但是让我说我​​的订购逻辑很复杂，我想只是重写关联获取器以实现我自己的逻辑

But let's say my ordering logic is complex and I want to just override the association getter to implement my own logic

我尝试类似-

class User < ActiveRecord::Base
  has_many :cars

  def cars
    # Pretend this is complex logic
    cars.order(:num_wheels)
  end
end

但是，这显然失败了，因为您无法引用原始的汽车从覆盖的 cars 方法内部，而不会无限循环。

However that obviously fails because you can't reference the original cars from inside the overridden cars method without it looping infinitely.

是否可以从覆盖的吸气剂内部引用原始吸气剂？

Is there a way to reference the "original" getter from inside my overridden getter?

谢谢！

推荐答案

使用超级：

class User < ActiveRecord::Base
  has_many :cars

  def cars
    # Pretend this is complex logic
    super.order(:num_wheels)
  end
end

当您使用像has_many这样的宏时，Rails动态创建一个模块（可以由在您的情况下，请定义访问器和读取器（在您的情况下，例如汽车，可以由User.genic_association_methods.instance_methods访问）。该模块成为您的User类的祖先，因此您可以在自己的cars方法中通过 super访问reader方法。

when you use a macro like has_many, Rails dynamically creates a module(which could be accessed by User.generated_association_methods).In your case, define the accessors and readers(such as "cars" in your case, which could be accessed by User.generated_association_methods.instance_methods). This module becomes the ancestor of your User class, so you can access the reader method(cars) by "super" in your own cars method.

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