python - 字段变化时如何调用类模型中的函数？

Question

在这个类中，当我添加帖子时，我想在类别字段更改时调用 category_change。

我怎样才能做到这一点？

class Post(models.Model):
    title = models.CharField(max_length=100)
    category = models.ForeignKey('Category', on_delete=models.CASCADE,null=True,blank=True,)
    image = models.ImageField(default='default.jpg', null=True, blank=True,editable=False)
    series = models.ForeignKey('Series', on_delete=models.CASCADE,null=True,blank=True,editable=False)
    tags = models.ManyToManyField('FilmTags', related_name='post')
    content = models.TextField()
    watch = models.TextField(null=True, default='')
    download_url = models.CharField(max_length=300, null=True, default="#")
    created = models.DateTimeField(default=timezone.now)
    updated = models.DateTimeField(auto_now=True)
    publish = models.BooleanField(default=True)
    views = models.IntegerField(default=0)

    def category_change(self):
        if category.title == "series":
            self.image.editable = True
            self.series.editable = True
            self.image = self.series.image
        else:
            self.image.editable = True

Answer 1

Django signals是你需要的。信号会通知您实例更改，类似于数据库触发器。演示在这里:

信号.py:

from django.db.models.signals import post_save
from django.dispatch import receiver

from .model import Post


@receiver(post_save, sender=Post)
def is_category_changed(sender, instance=None, created=False, **kwargs):
    instance.category_change()

应用程序.py:

from django.apps import AppConfig


class PostConfig(AppConfig):
    name = 'Post'
    verbose_name = 'Post'

    def ready(self):
        import post.signals # post is your app name