如何防止覆盖别人修改的对象 [英] How to prevent overwriting an object someone else has modified

问题描述

我想找到一种通用的方法来防止保存一个对象，如果它在保存后我检查出来。

I would like to find a generic way of preventing to save an object if it is saved after I checked it out.

我们可以假设对象有一个 timestamp 字段包含最后修改时间。如果我已经在 t1 签出（例如使用ModelForm访问视图），并且对象再次保存在 t2 ，给定 t2 > t1 我不能保存。

We can assume the object has a timestamp field that contains last modification time. If I had checked out (visited a view using a ModelForm for instance) at t1 and the object is saved again at t2, given t2 > t1 I shouldn't be able to save it.

推荐答案

覆盖首先检查最后一个时间戳的保存方法：

Overwrite the save method that would first check the last timestamp:

def save(self):
    if(self.id):
        foo = Foo.objects.get(pk=self.id)
        if(foo.timestamp > self.timestamp):
            raise Exception, "trying to save outdated Foo" 
    super(Foo, self).save()

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