Django如何檢查是否正在創建模型或創建或更新模型

Question

在不使用信號的情況下，是否可以在模型保存方法中檢查是否正在創建模型或創建或更新模型？ 如果可以，怎么辦？

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

您可以檢查是否已創建主鍵（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 ：當您檢查只有if id:它會被當作False時，如果id有值0 。 看一下這個：

>>> 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

這樣嘗試

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

   if self.id:
      # updated
   else:
      # inserted

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