Django - Overriding the Model.create() method?

user_175098 0
Viewed 89755

The Django docs only list examples for overriding save() and delete(). However, I'd like to define some extra processing for my models only when they are created. For anyone familiar with Rails, it would be the equivalent to creating a :before_create filter. Is this possible?

django-forms django-models django
7 Answers

Overriding __init__() would cause code to be executed whenever the python representation of object is instantiated. I don't know rails, but a :before_created filter sounds to me like it's code to be executed when the object is created in the database. If you want to execute code when a new object is created in the database, you should override save(), checking if the object has a pk attribute or not. The code would look something like this:

def save(self, *args, **kwargs):
    if not self.pk:
        # This code only happens if the objects is
        # not in the database yet. Otherwise it would
        # have pk
    super(MyModel, self).save(*args, **kwargs)
user_1833040

Overriding __init__() will allow you to execute code when the model is instantiated. Don't forget to call the parent's __init__().

Ignacio_Vazquez-Abrams_208620

The preferred answer is correct but the test to tell whether the object is being created doesn't work if your model derives from UUIDModel. The pk field will already have a value.

In this case, you can do this:

already_created = MyModel.objects.filter(pk=self.pk).exists()

user_63617580
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