Django 从 post_save 信号访问 ManyToMany 字段

使用 Django 开发网站时，经常会遇到需要在模型的 post_save 信号中访问 ManyToMany 字段的情况。在这篇文章中，我将介绍如何通过 post_save 信号来访问 ManyToMany 字段，并提供一个简单的案例代码来说明。

python
from django.db.models.signals import post_save
from django.dispatch import receiver
@receiver(post_save, sender=YourModel)
def your_signal_receiver(sender, instance, **kwargs):
    # 在这里访问 ManyToMany 字段
    pass

python
from django.db.models.fields.related import ManyToManyField
for field in instance._meta.get_fields():
    if isinstance(field, ManyToManyField):
        field_name = field.name
        field_value = getattr(instance, field_name)

python
from django.db import models
from django.db.models.signals import post_save
from django.dispatch import receiver
class Category(models.Model):
    name = models.CharField(max_length=100)
class Article(models.Model):
    title = models.CharField(max_length=100)
    categories = models.ManyToManyField(Category)
@receiver(post_save, sender=Article)
def update_categories(sender, instance, **kwargs):
    for category in instance.categories.all():
        print(category.name)