Django: Filter ModelChoiceField by user

Question

I have a model along with a ModelForm based on that model. The ModelForm contains a ModelMultipleChoice field, which I specify in the subclass of my ModelForm:

class TransactionForm(ModelForm):

    class Meta:
        model = Transaction

    def __init__(self, *args, **kwargs):
        super(TransactionForm, self).__init__(*args, **kwargs)
        self.fields['category'] = forms.ModelChoiceField(queryset=Category.objects.filter(user=user))

As you can see, I need to filter the Category queryset by user. In other words, users should only see their own categories on the drop down. But how can I do this when user, or more specifically, request.user, is not available in a Model instance?

Edit: Adding my subclass of the CBV:

class TransUpdateView(UpdateView):
    form_class = TransactionForm
    model = Transaction
    template_name = 'trans_form.html'
    success_url='/view_trans/'

    def get_context_data(self, **kwargs):
        context = super(TransUpdateView, self).get_context_data(**kwargs)
        context['action'] = 'update'
        return context

I tried form_class = TransactionForm(user=request.user) and I'm getting a NameError saying that request was not found.

Answer 1

You can pass request.user to form init in view:

def some_view(request):
     form = TransactionForm(user=request.user)

and add user parameter to form __init__ method (or pop it from kwargs in form):

class TransactionForm(ModelForm):
    class Meta:
        model = Transaction

    # def __init__(self, *args, **kwargs):
        # user = kwargs.pop('user', User.objects.get(pk_of_default_user))
    def __init__(self, user, *args, **kwargs):
        super(TransactionForm, self).__init__(*args, **kwargs)
        self.fields['category'] = forms.ModelChoiceField(
                                     queryset=Category.objects.filter(user=user))

update: in class based views you can add extra parameter to form init in get_form_kwargs:

class TransUpdateView(UpdateView):
    #...

    def get_form_kwargs(self):
        kwargs = super(YourView, self).get_form_kwargs()
        kwargs.update({'user': self.request.user})
        return kwargs