如何在Rails中组织复杂的回调？

Question

我有一个Rails应用程序,它使用了很多回调...所以我有很多函数被调用:after_create和:after_commit在多个模型中.

我想知道我现在这样做的方式是最好的.

基本上我有以下场景:

Class Parent < ActiveRecord::Base

has_many :children


after_create :first_function 
after_commit :last_function

    def first_function
        if !self.processed?
            self.children.create(:name => "Richard The Lion Heart")
            self.processed = true
            self.save!
        end
    end

    def last_function
        if self.processed?
            if !self.processing?
                self.process
                                    self.save!
                self.processing = true
                self.save!
            end
        end
    end

end

所以你可以看到整个事情取决于一些奇怪的双布尔检查,因为否则每次更新模型时都会调用second_function,并且它可以由函数本身更新,因此函数被重复调用.

总的来说,它引出了我必须为每个回调引入一个新的布尔检查的情况.它有效,但我不认为它优雅.我错过了什么？

Answer 1

你应该能够重写那些代码 - 像这样的东西？当然,您的真实代码可能还有一些额外的复杂性 - 另外:此代码未经测试.

Class Parent < ActiveRecord::Base
  has_many :children

  # only called when a new record is created
  after_create :first_function 

  # only called for updates, not new records, should still be inside the current transaction
  after_update :last_function

  private
    def first_function
      self.children.create(:name => "Richard The Lion Heart")
      # don't call save in here, already in a transaction
    end

    def last_function
      self.process
      # don't call save in here, already in a transaction        
    end

    def process
      # doing stuff ....
      self.children[0].update_attribute(:name, "Beowulf")
    end
end    

http://api.rubyonrails.org/classes/ActiveRecord/Callbacks.html

这总共有十二个回调,它为您提供了巨大的力量来为Active Record生命周期中的每个州做出反应和准备.为现有记录调用Base#save的顺序类似,只是每个_create回调都被相应的_update回调替换.

用法

p = Parent.new(:foo => "bar")
p.save
p.children[0].name
# => "Richard The Lion Heart"

p.update_attributes(:baz => "fud")
p.children[0].name
# => Beowulf

来自rails控制台的ActiveRecord回调(使用awesome_print ap)

> ap ActiveRecord::Callbacks::CALLBACKS
[
  [ 0] :after_initialize,
  [ 1] :after_find,
  [ 2] :after_touch,
  [ 3] :before_validation,
  [ 4] :after_validation,
  [ 5] :before_save,
  [ 6] :around_save,
  [ 7] :after_save,
  [ 8] :before_create,
  [ 9] :around_create,
  [10] :after_create,
  [11] :before_update,
  [12] :around_update,
  [13] :after_update,
  [14] :before_destroy,
  [15] :around_destroy,
  [16] :after_destroy,
  [17] :after_commit,
  [18] :after_rollback
]