[Answered ]-How to get only related objects in django serializer with manyToMany?

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A possibility here is to leverage a SerializerMethodField together with the serializer’s context object:

class BookingSerializer(serializers.ModelSerializer):
    class Meta:
        model = Booking
        fields = "__all__"


class EmployeeSerializer(serializers.ModelSerializer):
    bookings_st = serializers.SerializerMethodField()

    def get_bookings_st(self, employee):
        project = self.context.get("project")
        return BookingSerializer(
            employee.bookings_st.filter(project=project), 
            many=True,
        ).data

    class Meta:
        model = Employee
        fields = "__all__"


class ProjectSerializer(serializers.ModelSerializer):
    employees = serializers.SerializerMethodField()

    def get_employees(self, project):
        return EmployeeSerializer(
            project.employees.all(),
            many=True,
            context={**self.context, "project": project}
        ).data

    class Meta:
        model = Project
        fields = "__all__"

This wouldn’t be super performant if you’re using that when listing projects or when retrieving a specific project with many employees. Depending on your use case – if you’re only using it to retrieve a specific project, for example, you could leverage prefetch_related and the Prefetch class to prefetch custom employees + bookings querysets by filtering out the specific project at hand (and you could then use the regular serializers).

👤henriquesalvaro

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