在ActiveRecord中标记无效属性 [英] Flag invalid attribute in ActiveRecord

问题描述

我正在尝试实现以下功能：在ActiveRecord模型上，属性一旦设置就无法更改。为此，我编写了以下方法：

I am trying to implement functionality wherein an attribute, once set, cannot be changed on an ActiveRecord model. To this end, I have written the following methods:

def address
 self[:address]
end

def address=(val)
 if new_record?
  self[:address] = val
 else
  errors.add(:address, "Cannot change address, once it is set")
  return false # tried return nil here first, did not work
 end
end

我在这里做错了吗？尝试更改地址后，我希望该对象无效，但是当我执行 obj.valid？

Am I doing something wrong here? I want the object to be invalid once I try to change an address, but I do not get any errors when I do obj.valid?

编辑：设置后该值不会更改，但通过obj.valid进行验证时我想获取无效的对象吗？

The value is not changed once it is set, but I would like to get invalid object when I do the validation via obj.valid?

推荐答案

当您执行 obj.valid？时，它将清除所有错误，然后依次运行每个验证。要在验证时产生错误，您必须将该逻辑移至验证模块中。

When you do obj.valid?, it clears all of your errors, and then runs each of the validations in turn. To have this produce an error on validation, you'll have to move that logic into a validation block.

下面是使用实例变量执行此操作的一种示例：

Here's an example of one way to do that with an instance variable:

def address=(val)
  if new_record?
    self[:address] = val
  else
    @addr_change = true
    return false # tried return nil here first, did not work
  end
end

validate do |user|
  errors.add(:address, "Cannot change address, once it is set") if @addr_change
end

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