Django如何檢查模型是否正在創建或更新

Question

如果不使用信號，在模型保存方法中可以檢查模型是否正在創建或更新？如果是這樣如何？

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

嘗試這樣，

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

    if self.id: 
     # updated 
    else: 
     # inserted 

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

Answer 2

您可以檢查主鍵是否已經創建（即不無）：

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:它將被視爲False，以防止id的值爲0。看看這個：

>>> 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