Django drf序列化外键关联表ID以为字段

models.py

class Employees(BaseModel):
    email = models.EmailField(
        null=True,
        blank=True,
        verbose_name='员工邮箱'
    )
    name = models.CharField(
        max_length=128,
        verbose_name="员工姓名",
        null=True,
        blank=True
    )
    mobile = models.CharField(
        max_length=11,
        verbose_name="手机号",
        default="",
    )
    avatar = models.URLField(
        verbose_name="头像",
        blank=True,
        null=True,
        max_length=512,
        default=""
    )
    department = models.ForeignKey(
        to="Department",
        on_delete=models.SET_NULL,
        related_name="employees_in_department",
        verbose_name="关联部门表",
        null=True,
        blank=True
    )
    position = models.ForeignKey(
        to="EmployeesPosition",
        on_delete=models.SET_NULL,
        related_name="employees_in_position",
        verbose_name="关联职位表",
        null=True,
        blank=True
    )
    register_time = models.DateTimeField(
        auto_now_add=True,
        verbose_name="注册时间"
    )
    add_people = models.ForeignKey(
        User,
        verbose_name="添加者",
        related_name="linkadd_peoples",
        null=True,
        blank=True,
        on_delete=models.SET_NULL
    )
    connect_user = models.OneToOneField(to='User',
                                        verbose_name="员工关联用户表",
                                        null=True,
                                        blank=True,
                                        related_name="connect_employee",
                                        on_delete=models.SET_NULL
                                        )
    # EMPLOYEES_STATUS_OPEN = 0
    # EMPLOYEES_STATUS_CLOSE = 1
    # EMPLOYEES_STATUS_CHOICES = (
    #     (EMPLOYEES_STATUS_OPEN, 'open'),
    #     (EMPLOYEES_STATUS_CLOSE, 'close'),
    # )
    # status = models.PositiveSmallIntegerField(
    #     default=U,
    #     choices=User.USER_STATUS_CHOICES,
    #     help_text="{ 0:'open', 1:'close'}"
    # )

    class Meta:
        verbose_name = "员工表"
        verbose_name_plural = verbose_name

    def __str__(self):
        return self.name

    def get_status(self):
        if self.connect_user:
            return self.connect_user.status

        return User.USER_STATUS_INACTIVE

    def get_manage_departments(self):
        return self.manage_departments.filter(tags=0)

    def is_in_department(self, department_id):
        if self.department and self.department.id == department_id:
            return True

        return False

    def get_department_id(self):
        return getattr(self.department, 'id', -1)

    def is_department_leader(self):
        if self.department and self.department.is_header(self.id):
            return True

        return False

    def set_connect_user_inactive(self):
        if self.connect_user:
            return self.connect_user.set_inactive()

        return None

    @property
    def department_name(self):
        return self.department.departmentname

    @property
    def position_name(self):
        return self.position.positionname

    @property
    def add_people_name(self):
        return self.add_people.name


    def get_department_name(self):
        try:
            self.department.departmentname
        except Exception:
            return 'null'
        return self.department.departmentname

    def get_position_name(self):
        try:
            self.position.positionname
        except Exception:
            return 'null'
        return self.position.positionname

    def get_add_people_name(self):
        try:
            self.add_people.name
        except Exception:
            return 'null'
        return self.add_people.name

    def get_add_people_id(self):
        try:
            self.add_people.id
        except Exception:
            return 'null'
        return self.add_people.id

class EmployeesPosition(BaseModel):
    positionname = models.CharField(max_length=48,
                                    verbose_name="职位名称",
                                    unique=True)
    add_people = models.ForeignKey(User,
                                   verbose_name="员工职位添加者",
                                   null=True,
                                   blank=True,
                                   on_delete=models.SET_NULL,
                                   related_name="employee_position_add_people")
    fix_people = models.ForeignKey(User,
                                   verbose_name="最后修改者",
                                   null=True,
                                   blank=True,
                                   on_delete=models.SET_NULL,
                                   related_name="employee_position_fix_people")
    roles = models.ManyToManyField(to="Role",
                                   verbose_name="职位角色",
                                   blank=True,
                                   null=True)
    company = models.ForeignKey(to="Company",
                                verbose_name="公司职位表",
                                related_name="companys",
                                on_delete=models.SET_NULL,
                                null=True,
                                blank=True)

    class Meta:
        verbose_name = "员工职位表"
        verbose_name_plural = verbose_name

    def __str__(self):
        return self.positionname

    def employees_in_employeesposition(self):
        return self.employees_in_position.filter(tags=0)

    def get_employees_in_position(self):
        return self.employees_in_employeesposition.filter(id=self.employees_in_position.id).count() > 0

    def get_position_id(self):
        return getattr(self.employees_in_position, 'id', -1)

    @property
    def add_people_name(self):
        return self.add_people.name

    @property
    def fix_people_name(self):
        return self.fix_people.name

    @property
    def position_name(self):
        return self.positionname

serializer.py

class PositionSerializer(serializers.ModelSerializer):
    positionname = serializers.CharField(
        validators=[UniqueValidator(queryset=EmployeesPosition.objects.filter(tags=0))]
    )
    add_people_name = serializers.ReadOnlyField()
    fix_people_name = serializers.ReadOnlyField()
    position_name = serializers.ReadOnlyField()
    create_time = serializers.DateTimeField()
    fix_time = serializers.DateTimeField()
    class Meta:
        model = EmployeesPosition
        fields = ('id', 'positionname', 'add_people', 'fix_people', 'add_people_name', 'fix_people_name', 'position_name', "create_time", "fix_time")
        read_only_fields = ('id', 'add_people', 'fix_people',)
        extra_kwargs = {
            "positionname": {
                'required': True,
            }
        }

data

序列化外键以外字段