如何使用 manyToMany 仅获取 django 序列化程序中的相关对象？

Question

class BookingSerializer(serializers.ModelSerializer):

    class Meta:
        model = Booking
        fields = "__all__"


class EmployeeSerializer(serializers.ModelSerializer):
    bookings_st = BookingSerializer(many=True, read_only=True)

    class Meta:
        model = Employee
        fields = "__all__"


class ProjectSerializer(serializers.ModelSerializer):
    employees = EmployeeSerializer(read_only=True, many=True)

    class Meta:
        model = Project
        fields = "__all__"

class Employee(models.Model):
    name = models.CharField(max_length=127)
    lastname = models.CharField(max_length=127)


class Project(models.Model):
    title = models.CharField(max_length=127)
    employees = models.ManyToManyField(Employee,
                                       related_name='employees')

class Booking(models.Model):
    start = models.DateField()
    end = models.DateField()
    employee = models.ForeignKey(Employee,
                                 on_delete=models.CASCADE,
                                 related_name='bookings_st')
    project = models.ForeignKey(Project,
                                on_delete=models.CASCADE,
                                related_name='bookings_st')

我获得了嵌套对象，但是如何获得仅与（项目和员工）预订相关的员工？现在我只得到该员工的所有预订。我的意思是结构： project_1: emploee_1: [bookings_that_belong_to_THIS_PROJECT]

Answer 1

这里的一种可能性是利用 SerializerMethodField 和序列化程序的 context 对象：

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__"

如果您在列出项目或检索具有许多员工的特定项目时使用它，那么这不会是超级性能。根据您的用例 - 例如，如果您仅使用它来检索特定项目，您可以利用 prefetch_related 和 Prefetch class 来预取自定义员工 + 预订查询集过滤掉手头的特定项目（然后您可以使用常规序列化程序）。

如何使用 manyToMany 仅获取 django 序列化程序中的相关对象？

How to get only related objects in django serializer with manyToMany?

django

django-rest-framework