Django - how to test a clean form method, whether it's insert or update

Question

I have a form where I check in a clean method whether a ProjectMembership object exists that has the same values ​​for the project and member. This is because in the ProjectMembership model I defined a unique_together constraint for the project and member. Actually this works great.

class ProjectMembershipForm(forms.ModelForm): project = forms.ModelChoiceField(Project.objects, widget=HiddenInput()) class Meta: model = ProjectMembership def clean(self): cleaned_data = self.cleaned_data project = cleaned_data.get("project") member = cleaned_data.get("member") print ProjectMembership.objects.filter(project=project, member=member).count() if ProjectMembership.objects.filter(project=project, member=member).count() > 0: del cleaned_data["project"] del cleaned_data["member"] raise forms.ValidationError('The user "%s" is already part of the project team for project "%s".' % (member, project)) return cleaned_data 

But now I ask myself how can I judge by a pure method whether the user is trying to create a new relationship or update the relationship. Because using this clean method, it is not possible to perform an update because it returns an error message that the record already exists.

Answer 1

You can try changing this:

 if ProjectMembership.objects.filter(project=project, member=member).count() > 0: 

more or less like this:

 if ProjectMembership.objects.filter(project=project, member=member).exclude(pk=self.instance.id).count() > 0: 

in fact you need to check if self.instance is not None before using it in exclude, but hopefully this small snippet gave you an idea of ​​how you can accomplish your task without duplicating forms.

Answer 2

Try the following:

 if self.instance.pk: update_procedure() else: insert_procedure()