字段“id”需要一个数字，但得到了<QuerySet [<Department: GEE> ]&gt;

Question

I can't find the mistake here. I saw some similar questions but still can't fix it.

here is my models.py

class Department(models.Model):
    name = models.CharField(max_length=100)

class CustomUser(AbstractUser):
    department = models.ManyToManyField(Department, blank=True)

class Student(models.Model):
    user = models.OneToOneField(CustomUser, on_delete=models.CASCADE, primary_key=True)
    department = models.ManyToManyField(Department, blank=True)

forms.py

class StudentRegisterForm(UserCreationForm):
    class Meta(UserCreationForm):
        model = CustomUser
        fields = ['department', ..]
        widgets = {'department': forms.CheckboxSelectMultiple()}

    def __init__(self, *args, **kwargs):
        super(StudentRegisterForm, self).__init__(*args, **kwargs)
        self.fields['department'].required = True

    def clean_department(self):
        value = self.cleaned_data.get('department')
        if len(value) > 1:
            raise forms.ValidationError("You can't select more than one department!")
        return value

    def save(self, commit=True):
        user = super().save(commit=False)
        user.save()
        student = Student.objects.create(user=user)
        student.department.add(self.cleaned_data.get('department')) <-- got error on this line
        return (user, student)

When the CustomUser object is created, the Student object will also be created within save method. But for some reasons it gave me an error

TypeError: Field 'id' expected a number but got <QuerySet [<Department: GEE>]>.

Noticed that the Department objects were created within admin panel and also the department field within the Student model works just fine if I create it inside admin panel.

Answer 1

我通过将 * 添加到add方法中来修复它

student.department.add(*self.cleaned_data.get('department'))