How to add additional field in Django Rest Framework for a model that is a foreign key on another model

Question

I am looking to list out all of the teachers in a certain department in Django rest framework and am unsure of how to do so. I believe this would be done by adding a field to the Department serializer but I am not sure. Is there an easy way of how this can be done.

models.py

   class Department(models.Model):
       name = models.CharField(max_length=300)
    
        def __str__(self):
            return self.name
    
    
    class Teacher(models.Model):
        name = models.CharField(max_length=300)
        department = models.ForeignKey(Department, on_delete=models.CASCADE)
        tenure = models.BooleanField()

serializers.py

class DepartmentSerializer(serializers.HyperlinkedModelSerializer):
    #What I believe the serializer field would look like to list teachers connected 
    #with a department
    teacher = serializers.DjangoModelField(
        Teacher.objects.filter(department=self.department))

    class Meta:
        model = Department
        fields = ['url', 'name', 'teacher']

urls.py

router = DefaultRouter()
router.register(r'teachers', TeacherViewSet)
router.register(r'departments', DepartmentViewSet)
router.register(r'users', UserViewSet)

urlpatterns = [
    path('api/', include(router.urls)),
]

views.py

class TeacherViewSet(viewsets.ModelViewSet):
    queryset = Teacher.objects.all()
    serializer_class = TeacherSerializer
    permission_classes = [permissions.IsAuthenticatedOrReadOnly]


class DepartmentViewSet(viewsets.ModelViewSet):
    queryset = Department.objects.all()
    serializer_class = DepartmentSerializer
    permission_classes = [permissions.IsAuthenticatedOrReadOnly]

Answer 1

You can access the Teacher s linked to a department with mydepartment.teacher_set.all() , we can use that in the serializer like:

class TeacherSerializer(serializers.HyperlinkedModelSerializer):
    class Meta:
        model = Teacher
        fields = ['name', 'tenure']

class DepartmentSerializer(serializers.HyperlinkedModelSerializer):
    teacher_set = serializers.TeacherSerializer(many=True)

    class Meta:
        model = Department
        fields = ['url', 'name', 'teacher_set']