Set parent in a ModelForm in Google App Engine

Question

I want to create an Entity Group relationship in an Entity that is being created through a ModelForm.

How do I pass the parent instance and set the parent= attribute in the ModelForm?

Answer 1

I'll be interested to see if you get any good solutions to this problem. My own solution, which is far from elegant, is to do this:

book = models.Book(title='Foo')
chapter = models.Chapter(parent=book, title='dummy')
form = forms.ChapterForm(request.POST, request.FILES, instance=chapter)

Basically, I first create a dummy object (chapter in this case) with the correct parent relationship and then pass that as the instance argument to the form's constructor. The form will overwrite the throwaway data I used to create the dummy object with the data given in the request. At the end, to get the real child object, I do something like this:

if form.is_valid():
    chapter = form.save()
    # Now chapter.parent() == book