ruby-on-rails - ActiveRecord:方法名称作为符号传递时，不调用after_initialize

Question

我注意到当回调符号作为输入传递时，Rails不会触发after_initialize回调。

下面的代码不起作用。

class User < ActiveRecord::Base
  after_initialize :init_data

  def init_data
    puts "In init_data"
  end

end

下面的代码有效。

class User < ActiveRecord::Base

  def after_initialize 
    init_data
  end

  def init_data
    puts "In init_data"
  end
end

有人可以解释这种行为吗？

注意1

ActiveRecord documentation说了有关 after_initialize的以下内容:

Unlike all the other callbacks, after_find and after_initialize will 
only be run if an explicit implementation is defined (def after_find). 
In that case, all of the callback types will be called. 

虽然说after_initialize需要显式实现，但是我发现上一段中的第二句话是模棱两可的，即 In that case, all of
the callback types will be called.什么是 all of the call back types？

文档中的代码示例包含一个不使用显式实现的示例:

after_initialize EncryptionWrapper.new

Answer 1

根据documentation，您不能对after_initialize或after_find回调使用宏风格的类方法:

The after_initialize and after_find callbacks are a bit different from the others. They have no before_* counterparts, and the only way to register them is by defining them as regular methods. If you try to register after_initialize or after_find using macro-style class methods, they will just be ignored. This behaviour is due to performance reasons, since after_initialize and after_find will both be called for each record found in the database, significantly slowing down the queries.

简而言之，您必须定义一个 after_initialize实例方法:

class User < ActiveRecord::Base

  def after_initialize
    do_stuff
  end

end