Django在提交时创建一个额外的对象

Question

我试图在呈现页面后创建一个应答对象，当用户提供输入时，应答对象应该用新的输入更新并保存。我能够做到这一点，但由于某些原因，当用户单击submit按钮时，会创建一个额外的对象，而该对象始终为None。我使用AJAX从模板发送数据

views.py

def attention_view(request):
    participant = get_object_or_404(Participant, user=request.user)

    if request.method == 'POST':

        question_id = request.POST.get('assigned_question')
        question = get_object_or_404(Question, pk=question_id)
        answer = Answer.objects.get(participant=participant, question=question)

        if answer.answer is not None: 
            #preventing participants from changing their answer
            HttpResponse('')

        else:

            answer.answer = selected_choice
            answer.save()

    attention_question = Question.objects.get(id=13)
    answer = Answer.objects.create(participant=participant, question=attention_question)
    context = {'attention_question': attention_question, 'answer': answer}
    return render(request, 'study/AttentionCheck.html', context)

创建额外对象的原因可能是什么

Answer 1

你的逻辑是（简化的）：

    if request.method == 'POST':
        if answer.answer is not None: 
            # HttpResponse created and freed right away
            pass
        else:
            answer.answer = selected_choice
            answer.save()

    answer = Answer.objects.create(participant=participant,
      question=attention_question)

    return render(request, 'study/AttentionCheck.html', context)

请注意，1）始终调用Answer.objects.create2）始终返回呈现的AttentionCheck.html

我还注意到你在这里处理的是两个不同的问题：一个是邮寄的id问题，另一个是id为13的问题

根据您的具体要求，我认为这应该是解决方案：

def attention_view(request):
    participant = get_object_or_404(Participant, user=request.user)

    question = FIXME_WHICH_QUESTION

    answer, created = Answer.objects.get_or_create(participant=participant,
        question=question)

    if request.method == 'POST' and answer.answer is None: 
        answer.answer = selected_choice
        answer.save()

    context = {'attention_question': question, 'answer': answer}
    return render(request, 'study/AttentionCheck.html', context)