Django唯一性和关系约束

我正在使用django和django-rest框架编写一个RESTAPI。我现在正在写模型。

我有一个学生模型,一个问题模型和一个答案模型。

class Question(models.Model):
    question_text = models.CharField()


class Answer(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    answer_text = models.CharField()


class Student(models.Model):
    name = models.CharField()

学生们应该能够在每个问题上选择一个而且只有一个答案。所以我想设计一个学生选择的答案模型-这样我就可以让学生选择一个关系-就像这样:

class StudentPickedAnswer(models.Model):
    student = models.ForeignKey(Student, on_delete=models.CASCADE)
    answer = models.ForeignKey(Answer, on_delete=models.CASCADE)

我发现有一个 unique_together 的约束 class Meta . 但在我看来,它不能具体说明关系。我需要这样的东西;

class Meta:
   unique_together = ('student', 'answer__question')

我怎样才能做到学生每个答案只能选一个问题?或者挑选一个有关系的模型是一个糟糕的设计?

class Question(models.Model): question_text = models.CharField() options = models.ManyToManyField(QuestionOption) class QuestionOption(models.Model): option_text = models.CharField(max_length=255) class Student(models.Model): name = models.CharField() class StudentResponse(models.Model): student = models.ForeignKey(Student) question = models.ForeignKey(Question) response_option = models.ForeignKey(QuestionOption) class Meta: unique_together = ("student", "question")

class Question(models.Model): question = models.CharField(...) class QuestionOption(models.Model): question = models.ForeignKey("Question",related_name="qs_options") option = models.CharField(max_length=200) class Meta: # ensuring choices are not duplicated for a question. unique_together = ("question", "option")