通過視圖更新相關的 model 字段（Django REST）

Question

class Question(models.Model):
   ...
   posted_by = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
   # following fields are for sorting by popularity
   popular_param = models.BigIntegerField(default=0)

class Answer(models.Model):
   question = models.ForeignKey(Question, related_name='answers', on_delete=models.CASCADE)
   ...
   posted_by = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)

我想要實現的目標：每當創建一個答案時，問題model的 Popular_param 應該增加 10。

我通過覆蓋視圖集中的perform_create嘗試了以下操作。

class PostAnswerViewSet(viewsets.ModelViewSet):
    """
    this is where you post answers
    """
    queryset = Answer.objects.all()
    serializer_class = PostAnswerSerializer

    def perform_create(self, serializer):
        answer = self.get_object()
        answer.question.popular_param = F('popular_param') + 10
        answer.question.save()
        serializer.save()

或者

    def perform_create(self, serializer):
        Answer.question.popular_param = F('popular_param') + 10
        Answer.question.save()
        serializer.save()

我似乎遺漏了一些語法，但不知道是什么。 到目前為止，關於 SO 的其他問題都沒有幫助。

Answer 1

你可以試試這個：

class PostAnswerViewSet(viewsets.ModelViewSet):
    """
    this is where you post answers
    """
    queryset = Answer.objects.all()
    serializer_class = PostAnswerSerializer

    def perform_create(self, serializer):
        answer = serializer.save()
        answer.question.popular_param = F('popular_param') + 10
        answer.question.save()

因為在調用serializer.save()時將創建Answer object 。 在此之前，我認為我們不能get_object() 。