django ValueError 无法查询“abcd@gmail.com”：必须是“对象”实例

Question

我正在尝试为学生制作应用程序，但出现此错误， 如您所见，为了方便起见，我想像下面展示的那样使用它，但是它不起作用，我应该像以前一样继续使用吗？或者我可以这样使用？最好的方法是什么？

/student/program_structure/ 处的值错误 无法查询“abcd@gmail.com”：必须是“学生”实例。

非常感谢:)

models.py

class Student(models.Model):
    user = models.ForeignKey(
          settings.AUTH_USER_MODEL, on_delete=models.CASCADE, null=True)
    status = models.CharField(max_length=10, choices=STATUS, default='active')
 
 
class Program(models.Model):
        
         #everything was fine when used 

    user = models.ForeignKey(
          settings.AUTH_USER_MODEL, on_delete=models.CASCADE, null=True)  #this one

         #but when using this one i started getting this error from views.py 

    user = models.ForeignKey(
                  Student, on_delete=models.SET_NULL, null=True)

    name = models.CharField(max_length=200, unique=True)
    prefix = models.CharField(max_length=20)


class Course(models.Model):
    user = models.ForeignKey(Student, on_delete=models.SET_NULL, null=True)
    name = models.CharField(max_length=200, unique=True)
    prefix = models.CharField(max_length=20)
    code = models.CharField(max_length=20)

   subject = models.ManyToManyField('Subject', related_name='subject_list', 
                  blank=True)


views.py
       

class Program_structure(generic.View):

    def get(self, *args, **kwargs):
        profile = get_object_or_404(Student, user=self.request.user)
        program_structure = Course.objects.filter(student=profile)
         # program_structure = 
        Course.objects.filter(student__user=self.request.user)


        credit = Course.objects.filter(student__user=self.request.user).
           annotate(total_no=Sum('subject__credit'))

        total_credit = self.request.user.course_set.aggregate(
             total_credit=Sum('subject__credit')
           )['total_credit'] or 0

     context = {
        'test':program_structure,
        'credit':credit,
        'profile':profile,
        'total_credit' : total_credit
    }
    return render(self.request, 'program_structure.html', context)

Answer 1

Course 的user 字段指的是Student 对象，而不是User 对象，因此您不能为此使用request.user。

但是，您可以通过以下方式查询Course，其中user 是Student，其中user 是request.user：

class Program_structure(generic.View):

    def get(self, *args, **kwargs):
        profile = Student.objects.all()
        program_structure = Course.objects.filter(user__user=self.request.user)
        context = {
           'test':program_structure,
           'profile':profile,
        }
        return render(self.request, 'program_structure.html', context)

您可能还想将profile 设置为用户的Student 对象。在这种情况下，您可以在过滤 Courses 时重用 profile：

from django.shortcuts import get_object_or_404

class Program_structure(generic.View):

    def get(self, *args, **kwargs):
        profile = get_object_or_404(Student, user=request.user)
        program_structure = Course.objects.filter(user=profile)
        context = {
           'test':program_structure,
            'profile':profile,
        }
        return render(self.request, 'program_structure.html', context)

最好将user 字段重命名为student：

class Course(models.Model):
    student = models.ForeignKey(
        Student,
        on_delete=models.SET_NULL,
        null=True
    )
    # …

因为这表明这是Student，而不是User。在这种情况下，您可以使用以下内容进行过滤：

from django.shortcuts import get_object_or_404

class Program_structure(generic.View):

    def get(self, *args, **kwargs):
        profile = get_object_or_404(Student, user=request.user)
        program_structure = Course.objects.filter(student=profile)
        context = {
           'test':program_structure,
            'profile':profile,
        }
        return render(self.request, 'program_structure.html', context)