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Python

Lars Wettmann
Lars Wettmann
15,376 Points
Posted by Lars Wettmann
Lars Wettmann
15,376 Points

How to update model and fields in Class Based Views based on pk?

Hi guys,

I try to re-write this https://teamtreehouse.com/library/django-forms/model-forms/handling-multiple-form-classes to a class based view.

Basically what I am trying to do is get a "mc" or "tf" pk via the URL and change the model and fields of my CreateView based on that.

It seems that the question_type in get() can be found, but the models and fields don't get changed. I tried to look it up at CCBV but I cannot understand anything from that sort of documentation.

The pk is called "question_type". This is my View:

class QuestionCreateView(LoginRequiredMixin, mixins.PageTitleMixin, CreateView):
        #setting standard model and fields
    model       =   models.MultipleChoiceQuestion 
    fields      =   ('quiz','order', 'prompt', 'shuffle_answers')
    page_title          =   "Add a new Question"
    context_object_name =   "quiz"
    template_name       =   "courses/question_form.html"

    def get_context_data(self, **kwargs):
        ''' only used for the page title '''
        context             =   super().get_context_data(**kwargs)
        context['quiz']     =   models.Quiz.objects.filter(id=self.kwargs['quiz_pk']).first()
        return context

    def get(self, request, *args, **kwargs):
        get     =   super().get(request, args, kwargs)
        question_type = kwargs.get('question_type')
        self.set_question_type(question_type)
        return get

    def set_question_type(self, question_type):
        if question_type == 'tf': 
            self.model      =   models.TrueFalseQuestion
            self.fields     =   ('quiz','order', 'prompt', 'correct_answer')
        else:
            self.model      =   models.MultipleChoiceQuestion
            self.fields     =   ('quiz','order', 'prompt', 'shuffle_answers')
        return True

I'm happy for every help. I'm struggling on this topic since days. Thanks in advance.

1 Answer

Lars Wettmann
Lars Wettmann
15,376 Points
Lars Wettmann
Lars Wettmann
15,376 Points

Okay, miraculously, I found the answer myself just now. For everyone who's bumping into the same problem:

Basically, all control structures need to go into a separate method. You override the dispatch() method, get the kwargs, and call your own method to run the control structure and update the class attributes.

class QuestionCreateView(LoginRequiredMixin, mixins.PageTitleMixin, CreateView):
    question_type       =   ""
    page_title          =   "Add a new Question"
    context_object_name =   "quiz"
    template_name       =   "courses/question_form.html"

    def set_question_type(self, question_type):
        if question_type == 'tf': 
            self.model      =   models.TrueFalseQuestion
            self.fields     =   ('quiz','order', 'prompt', 'correct_answer')
        else:
            self.model      =   models.MultipleChoiceQuestion
            self.fields     =   ('quiz','order', 'prompt', 'shuffle_answers')
        return True

    def get_context_data(self, **kwargs):
        ''' only used for the page title '''
        context             =   super().get_context_data(**kwargs)
        context['quiz']     =   models.Quiz.objects.filter(id=self.kwargs['quiz_pk']).first()
        return context

    def dispatch(self, request, *args, **kwargs):
        question_type = kwargs.get('question_type')
        self.set_question_type(question_type)
        # call the view
        return super().dispatch(request, *args, **kwargs)