Django如何检查是否正在创建模型或创建或更新模型

Question

在不使用信号的情况下，是否可以在模型保存方法中检查是否正在创建模型或创建或更新模型？ 如果可以，怎么办？

def save(self, force_insert=False, force_update=False, *args, **kwargs):
        """
        Override of save() method which is executed the same
        time the ``pre_save``-signal would be
        """

        models.Model.save(self, *args, **kwargs)

Answer 1

您可以检查是否已创建主键（即不是None ）：

def save(self, force_insert=False, force_update=False, *args, **kwargs):

    if self.pk is None:
        # model is going to be created
    else:
        # model will be updated

    super(YourModelClass, self).save(*args, **kwargs)

注意 ：当您检查只有if id:它会被当作False时，如果id有值0 。 看一下这个：

>>> id = 0
>>> if id:
...     print("ID is set to %s" % id)
... # no result, but the value is set!

>>> id = 1
>>> if id:
...     print("ID is set to %s" % id)
...
ID is set to 1

>>> id = 0
>>> if id is not None:
...     print("ID is set to %s" % id)
...
ID is set to 0

Answer 2

这样尝试

def save(self, force_insert=False, force_update=False, *args, **kwargs):

   if self.id:
      # updated
   else:
      # inserted

   models.Model.save(self, *args, **kwargs)