Nested Serializer Not Working in django rest framework. How can I fix it?

February 20, 2023

Can you tell me where is the actual problem?
My goal is to build up an API that will show how many courses an instructor offers.

models.py:

class Instructor(models.Model):
    name = models.CharField(max_length=40)
    email = models.CharField(max_length=250)


class Course(models.Model):
    Title = models.CharField(max_length=250)
    Instructor = models.ForeignKey(Instructor, on_delete=models.CASCADE, related_name="CourseInstructorRelatedNAme")

Serializer.py:

class CourseSerializer(ModelSerializer):
    class Meta:
        model = Course
        fields = '__all__'

class InstructorSerializer(ModelSerializer):

    courses = CourseSerializer(many=True, read_only=True)
    class Meta:
        model = Instructor
        fields = '__all__'

views.py:

class CourseViewSet(ModelViewSet):
    serializer_class = CourseSerializer
    queryset = Course.objects.all()

class InstructorViewSet(ModelViewSet):
    serializer_class = InstructorSerializer
    queryset = Instructor.objects.all()

urls.py:

router.register(r"course", views.CourseViewSet , basename="course")
router.register(r"instructor", views.InstructorViewSet , basename="instructor")

>Solution :

The related_name is the name you of the reverse relation you have to use if you want to access the items from the parent object.

If you want to retrieve your queryset of courses as courses, you need to change the related_name in your model:

# models.py
class Course(models.Model):
    Title = models.CharField(max_length=250)
    Instructor = models.ForeignKey(Instructor, on_delete=models.CASCADE, related_name="courses")