Django 管理员过滤器外键组合框

Question

我是 django 初学者，所以代码可能是基本的或错误的，但无论如何......我有以下型号：

 from django.db import models
    from django.conf import settings
    GRADE_CHOICES = (
        ('1', '1'),
        ('2', '2'),
        ('3', '3'),
        ('4', '4'),
        ('5', '5'),
        ('6', '6'),
        ('7', '7'),
        ('8', '8'),
        ('9', '9'),
        ('10', '10'),
    )
    class Professor(models.Model):
        first_name = models.CharField(max_length=20)
        last_name = models.CharField(max_length=30)
        def __str__(self):
            rta = self.first_name+" "+self.last_name
            return rta
    class Student(models.Model):
        first_name = models.CharField(max_length=20, blank=False, null=False)
        last_name = models.CharField(max_length=30, blank=False, null=False)
        def __str__(self):
            rta = self.first_name+" "+self.last_name
            return rta
    class Subject(models.Model):
        first_name = models.CharField(max_length=50)
        students = models.ManyToManyField(Student, blank=True)
        professors = models.ManyToManyField(Professor, blank=True)
        def __str__(self):
            return self.first_name
    class Grade(models.Model):
        value = models.CharField(choices=GRADE_CHOICES, max_length= 2)
        subject = models.ForeignKey(Grade, on_delete=models.CASCADE, related_name='fk_grade')
        student = models.ForeignKey(Student, on_delete=models.CASCADE, related_name='fk_student')
        def __str__(self):
            return self.value

要添加成绩，我需要选择科目和学生，因此我想根据学生所属的科目过滤学生。如果学生不在那个科目中，他不应该出现在列表中。

我使用的是 django 1.11 和 python 2.7。

Answer 1

您的对象Grade不应与Subject和Student相关，而应与Subject和Student之间的关系相关。Sometinhg like：

class Professor(models.Model):
    # ...
class Student(models.Model):
    # ...
    professors = models.ManyToManyField(Person, through='Subject')

class Subject(models.Model):
    name = models.CharField(max_length=50)
    student = models.ForeignKey(Student, on_delete=models.CASCADE)
    professor = models.ForeignKey(Professor, on_delete=models.CASCADE)
    value = models.CharField(choices=GRADE_CHOICES, max_length= 2)