在 Django 中为多对多字段冲突反向访问器和查询？

Posted 2023-02-24

【中文标题】在 Django 中为多对多字段冲突反向访问器和查询？

【英文标题】：***ing reverse accessors and queries in Django for many to many field?

【发布时间】：2021-07-15 09:59:29

【问题描述】：

from django.db import models


class Appointment(models.Model):
    doctors = models.ManyToManyField('Doctor', through='AppointmentAccess', related_name='appointments')


class Doctor(models.Model):
    appointments = models.ManyToManyField('Appointment', through='AppointmentAccess', related_name='doctors')

我收到以下错误：

core.Appointments.doctors: (fields.E302) Reverse accessor for 'PatientProfile.users' ***es with field name 'Doctor.appointments'.
        HINT: Rename field 'Doctor.appointments', or add/change a related_name argument to the definition for field 'Appointment.doctors'.
core.Appointment.doctors: (fields.E303) Reverse query name for 'Doctor.appointments' ***es with field name 'Appointment.doctors'.
        HINT: Rename field 'Doctor.appointments', or add/change a related_name argument to the definition for field 'Appointment.doctors'.
core.Doctor.appointments: (fields.E302) Reverse accessor for 'Doctor.appointments' ***es with field name 'Appointments.doctors'.
        HINT: Rename field 'Appointment.doctors', or add/change a related_name argument to the definition for field 'Doctor.appointments'.
core.User.patient_profiles: (fields.E303) Reverse query name for 'Doctor.appointments' ***es with field name 'Appointments.doctors'.
        HINT: Rename field 'Appointments.doctors', or add/change a related_name argument to the definition for field 'Doctor.appointments'.

为什么？有人可以帮我理解这个错误吗？应该通过 AppointmentAccess 表跟踪多对多字段，而不是生成新的中间表。相关姓名预约与医生有何冲突？

【问题讨论】：

为什么两个模型都需要指定m2m？只需在其中一个中指定即可。

【参考方案1】：

您在两个模型中都指定了多对多关系。这不是必需的，因为 Django 会自动向关系中的其他模型添加反向关系，因此您可以简单地编写：

class Appointment(models.Model):
    # Remove below line
    doctors = models.ManyToManyField('Doctor', through='AppointmentAccess', related_name='appointments')
    ...


class Doctor(models.Model):
    appointments = models.ManyToManyField('Appointment', through='AppointmentAccess', related_name='doctors')

现在既然你已经设置了related_name（如果你没有默认设置为doctor_set，即小写的型号名称）如果你有一个Appointment的实例appointment你可以简单地写：

for doctor in appointment.doctors.all():
    print(doctor)