python - django 'auto_now' 如何忽略指定字段的更新

Question

我有一个模型，如下所示:

    name = models.CharField(max_length=255)
    modify_time = models.DateTimeField(auto_now=True)
    chasha = models.CharField(max_length=255)
    stat = models.CharField(max_length=255)

通常，当我更新“name”、“chasha”、“stat”字段时，“modify_time”也会更新。但是，我只是不想在更新“stat”时更新“modify_time”。我该怎么做？

谢谢。

Answer 1

使用自定义保存方法通过查看以前的实例来更新字段。

from django.db import models
from django.utils import timezone as tz


class MyModel(models.Model):
    name = models.CharField(max_length=255)
    modify_time = models.DateTimeField(null=True, blank=True)
    chasha = models.CharField(max_length=255)
    stat = models.CharField(max_length=255)

    def save(self, *args, **kwargs):
        if self.pk: # object already exists in db
            old_model = MyModel.objects.get(pk=self.pk)
            for i in ('name', 'chasha'): # check for name or chasha changes
                if getattr(old_model, i, None) != getattr(self, i, None):
                    self.modify_time = tz.now() # assign modify_time
        else: 
             self.modify_time = tz.now() # if new save, write modify_time
        super(MyModel, self).save(*args, **kwargs) # call the inherited save method

编辑:像上面一样从modify_time中删除auto_now，否则它将在保存方法中设置。