Test if Django ModelForm has instance

Question

I would like to display a warning message if I am into an editing form and hide it if I am in a creation form of a Django ModelForm.

form.is_bound tell me if the form was previously populated but how to test if the ModelForm was set with an existing instance ?

I tried this hasattr(form.instance, 'pk') but is it the right way to do so ?

Cheers,

Natim

Answer 1

Try checking if form.instance.pk is None.

hasattr(form.instance, 'pk') will always return True, because every model instance has a pk field, even when it has not yet been saved to the database.

As pointed out by @Paullo in the comments, this will not work if you manually define your primary key and specify a default, e.g. default=uuid.uuid4.

Answer 2

Since the existed instance would be passed as an argument with the keyword instance to create the model-form, you can observe this in your custom initializer.

class Foo(ModelForm):     _newly_created: bool      def __init__(self, *args, **kwargs):         self._newly_created = kwargs.get('instance') is None         super().__init__(*args, **kwargs)