小编Ale*_*dev的帖子

我想在我的django应用程序中为每个模型添加几个字段.这次是created_at,updated_at和notes.20个模型中每个模型的复制代码似乎都很愚蠢.所以,我决定使用抽象基类来添加这些字段.问题是从抽象基类继承的字段首先出现在admin的字段列表中.声明每个ModelAdmin类的字段顺序不是一个选项,它甚至比手动字段声明更重复代码.

在我的最终解决方案中,我修改了模型构造函数以在创建新实例之前重新排序_meta中的字段:

class MyModel(models.Model):
    # Service fields
    notes = my_fields.NotesField()
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        abstract = True

    last_fields = ("notes", "created_at", "updated_at")
    def __init__(self, *args, **kwargs):
        new_order = [f.name for f in self._meta.fields]
        for field in self.last_fields:
            new_order.remove(field)
            new_order.append(field)
        self._meta._field_name_cache.sort(key=lambda x: new_order.index(x.name))
        super(MyModel, self).__init__(*args, **kwargs)

class ModelA(MyModel):
    field1 = models.CharField()
    field2 = models.CharField()
    #etc ... 

它按预期工作,但我想知道,有没有更好的方法来实现我的目标？

尝试以最干净的方式向我的应用添加电子邮件通知.当模型的某些字段发生变化时,应该向用户发送通知.这是我的旧解决方案:

from django.contrib.auth import User

class MyModel(models.Model):
    user = models.ForeignKey(User)
    field_a = models.CharField()
    field_b = models.CharField()

    def save(self, *args, **kwargs):
        old = self.__class__.objects.get(pk=self.pk) if self.pk else None
        super(MyModel, self).save(*args, **kwargs)
        if old and old.field_b != self.field_b:
            self.notify("b-changed")
        # Sevelar more events here
        # ...

    def notify(self, event)
        subj, text = self._prepare_notification(event)
        send_mail(subj, body, settings.DEFAULT_FROM_EMAIL, [self.user.email], fail_silently=True)

这个工作正常,而我有一两种通知类型,但之后我觉得在我的save()方法中有这么多代码感觉不对.所以,我将代码更改为基于信号:

from django.db.models import signals

def remember_old(sender, instance, **kwargs):
    """pre_save hanlder to save clean copy of original record into `old` attribute
    """ …