django - 在模板中扩展 ManyToManyField

Question

我需要创建一个有一些选项的 manytomany 字段，然后在每个选项旁边有一个额外的字段
我的模型:

class Subject(models.Model):
    name = models.CharField(max_length=30)
    duration = models.IntegerField()
    price = models.IntegerField()

class Student(models.Model):
    firstname = models.CharField(max_length=30)
    lastname = models.CharField(max_length=30)
    subject = models.ManyToManyField(Subject,through="StudentSubject")

class StudentSubject(models.Model)
    student = models.ForeignKey(Student,on_delete=models.CASCADE)
    subject = models.ForeignKey(Subject,on_delete=models.CASCADE)
    discount = models.IntegerField()

我使用了中间模型 StudentSubject(它包含额外的字段)，但我不确定我应该如何在模板中呈现它，我想做这样的事情:

Math DiscountField1
Physics DiscountField2
CompSci DiscountField3

Answer 1

您可以枚举StudentSubject所以对于学生来说，你可以:

{% for studentsubject in mystudent.studentsubject_set.all %}
    {{ studentsubject.subject.name }} {{ studentsubject.discount }}
{% endfor %}

与 mystudent ，您为其列出具有相应折扣的科目的学生。
您可以通过在 View 中预取和选择相关对象来提高效率，因此:

from django.db.models import Prefetch
from django.shortcuts import render

def my_view(request, pk):
    qs = Student.objects.prefetch_related(
        Prefetch(
            'studentsubject_set',
            queryset=StudentSubject.objects.select_related('subject')
        )
    )
    mystudent = get_object_or_404(qs, pk=pk)
    # …
    return render(request, 'some-template.html', {'mystudent': mystudent})