Mongoid 3 回调：before_upsert 与 before_save

Question

对于 Mongoid 3+，是否有各种回调的图表/描述？ http://mongoid.org/en/mongoid/v3/callbacks.html

例如，

before_upsert

与

before_save

之间有什么区别。

save

不是由

insert

或

update

调用引起的吗？还是

save

也被

destroy

调用？

还有，

before_xxx

和

around_xxx

有什么区别？

Answer 1

使用 before_xxx，代码在动作之前执行，使用 around_xxx，您可以选择在动作本身之前和之后执行代码。

例如，假设您想在销毁用户项目后更新所有用户所有物（User has_many :proyects and Project belongs_to User）：

class ProjectsController < ApplicationController

  around_destroy :destroy_belongings

  def destroy_belongings
    old_user = self.user
    ...
    # Here the before_destroy ends.

    yield # Here the destroy is performed itself.

    # Here the after_destroy starts. It's needed to do this operation after destroy the project because, imagine, the update_belongings method calculates something related to the current number of proyects. And a simple after_destroy is not useful as we would have lost the project owner.

    old_user.update_belongings
  end
end

您还可以在这里和这里看到相关答案。此外另一篇文章可能对你有用。