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Updating foreign key field in Django

I have a form displaying a dropdown for a foreignkey field. The form saves the users' selections, however I want the view to update the database record instead of inserting a new one. What's the best way to do this?

Current function:

def formset_valid(self, formset):
    self.object = formset.save()
    self.object.save()
    return HttpResponseRedirect(self.get_success_url())

I've tried something like this:

d = RevisionDefaultType.objects.get(id=1)
n = RevisionSettings.objects.get(self.object)
d.defaultrevisiontype = n
d.save()

But it throws an error that the data being updated is not an instance.

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2 answers


I was able to customize the update example from https://docs.djangoproject.com/en/dev/topics/db/queries/#saving-foreignkey-and-manytomanyfield-fields . This seems to work as desired.

    def formset_valid(self, formset):

        self.object = formset.save(commit=False)
        revdefault = RevisionDefaultType.objects.get(pk=1)
        revget = RevisionSettings.objects.get(global_revision_type=self.object)
        revdefault.defaultrevisiontype = revget
        revdefault.save()

        return HttpResponseRedirect(self.get_success_url())


Thanks again for your help.

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You have to add force_update=True

to your function save()

.



For more information on How Django knows UPDATE vs. INSERT , see this link in django documentation.

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