Ruby on Rails - before_action with condition only when an attribute has been changed

Question

在我的应用程序中，我 Post 具有属性 title 和 price 等的模型

我有 2 个 before_action 我想运行只有当 title 改变时和另一个 仅当 price 已更改时 。

class Post < ActiveRecord::Base

  before_update :do_something_with_title
  before_update :do_something_with_price

  def do_something_with_title
    // my code for title here
  end

  def do_something_with_price?
    // my code for price here
  end

我知道我可以使用 changed? 并给 before_action 一个 if: 条件，但这将适用于 post 中的任何属性发生变化时，而不仅仅是 title & price 已更改。

感谢任何帮助！

Answer 1

您可以使用 title_changed? 或 price_changed?

class Post < ActiveRecord::Base    
  before_update :do_something_with_title, if: :title_changed?
  before_update :do_something_with_price, if: :price_changed?
end

Answer 2

您可以使用

class Post < ActiveRecord::Base    
  before_update :do_something_with_title, if: :title_changed?
  before_update :do_something_with_price, if: :price_changed?
  ...
end

或

class Post < ActiveRecord::Base    
  before_update { |post| post.do_something_with_title if post.title_changed? }
  before_update { |post| post.do_something_with_price if post.price_changed? }
  ...
end

Ruby on Rails - before_action with condition only when an attribute has been changed

Ruby on Rails - before_action with condition only when one attribute has been changed

ruby

model

before-filter

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