问题描述
当在控制台中使用自动完成，我经常看到 _was postpended我的属性。但是，我找不到任何使用或文件的最佳实践。它是干什么的以及应当如何使用？
When using autocomplete in the console, I often see "_was" postpended to my attributes. But I can't find any documentation or best practices for usage. What does it do and how should it be used?
例如： user.fname 的方法 user.fname_was
使用源位置，我已经跟踪它到：active_model / attribute_methods.rb，线路296，但没有任何具体的
Using source_location, I've tracked it down to: active_model/attribute_methods.rb", line 296 but there isn't anything specific.
推荐答案
这是加载ActiveModel的一部分::脏在这里你可以看到它https://github.com/rails/rails/blob/af64ac4e5ce8406137d5520fa88e8f652ab703e9/activemodel/lib/active_model/dirty.rb#L146示例
That is a part of ActiveModel::DirtyYou can see it here https://github.com/rails/rails/blob/af64ac4e5ce8406137d5520fa88e8f652ab703e9/activemodel/lib/active_model/dirty.rb#L146Example
person = Person.find_by_name('Uncle Bob')
person.changed? # => false
更改名称：
person.name = 'Bob'
person.changed? # => true
person.name_changed? # => true
#method _was return prev attribute value
person.name_was # => 'Uncle Bob'
person.name_change # => ['Uncle Bob', 'Bob']
person.name = 'Bill'
person.name_change # => ['Uncle Bob', 'Bill']
这篇关于什么是加载ActiveModel方法属性和QUOT; _was＆QUOT;用于？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！