是否有在ActiveRecord的'重装'复位实例变量干净的API？ [英] Is there a clean API for resetting instance variables on 'reload' in ActiveRecord?
问题描述
在的ActiveRecord :: Base的模式，我可以重置模型的状态，这是什么，当我得到了它从数据库重装，只要属性我设置映射到表列：
In an ActiveRecord::Base model, I can reset the state of the model to what it was when I got it from the database with reload, as long as the attribute I'm setting maps to a table column:
user = User.first
user.email #=> "email@domain.com"
user.email = "example@site.com"
user.email #=> "example@site.com"
user.reload
user.email #=> "email@domain.com"
但是，如果我添加自定义属性，只有这样，我发现有它的行为同样是这样的：
But if I add a custom attribute, the only way I've found to have it act the same is like this:
class User < ActiveRecord::Base
attr_accessor :user_agent
def reload
super
self.user_agent = nil
self
end
end
我的问题是，有没有一些API，使非数据库列的属性重置重装？是这样的：
My question is, is there some API to make non-database-column-attributes reset on reload? Something like:
class User < ActiveRecord::Base
# this
reloadable_attr_accessor :user_agent
# or this
def user_agent
@user_agent
end
def user_agent=(value)
set_instance_var_that_resets_on_reload("@user_agent", value)
end
end
确实存在于Rails的那个地方？
Does that exist in Rails somewhere?
推荐答案
的ActiveRecord不提供一种方式来做到这一点，对模型的属性就只能充当。
ActiveRecord does not provide a way to do this, it can only acts on the model attributes.
话虽这么说，我觉得更优雅的方式来做到这一点会遍历所有的实例变量，并将其设置为任何你喜欢的：
That being said, I think a more elegant way to do it would be to loop over the ivars and set them to whatever you like :
class User < ActiveRecord::Base
def reload(options = nil)
super
self.instance_variables.each do |ivar|
next if ivar == '@attributes'
self.instance_variable_set(ivar, nil)
end
end
end
请注意，我们跳过@属性，因为AR是照顾它，当你重新加载的属性。
Note that we skip @attributes because AR is taking care of it when you reload the attributes.
这篇关于是否有在ActiveRecord的'重装'复位实例变量干净的API？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
