在 Django 中向多个模型添加常见 date_added、date_modified 的最佳方法
我将 date_added 和 date_modified 字段添加到当前项目中的一堆常见模型中。我正在子类化 models.Model 并添加适当的字段，但我想添加自动保存行为（即：每次有人调用 MyModel.save() 时，date_modified 字段都会更新。我看到两种方法：覆盖 save() 方法或者在抽象基类中添加 pre_save 信号处理程序，
class CommonData(models.Model):
date_added = models.DateTimeField(default=datetime.datetime.today,null=False,blank=False)
date_modified = models.DateTimeField(default=datetime.datetime.today,null=True,blank=True)
# register a handler for the pre_save to update date_modified
def pre_save_handler(sender, **kwargs):
date_modified = datetime.datetime.today
def __init__():
pre_save.connect(pre_save_handler, sender=self)
或者
class CommonData(models.Model):
date_added = models.DateTimeField(default=datetime.datetime.today,null=False,blank=False)
date_modified = models.DateTimeField(default=datetime.datetime.today,null=True,blank=True)
# overriding save
def save(force_insert=False,force_update=False):
date_modified = datetime.datetime.now
return models.Model.save(force_insert, force_update)
我是 Django 和 Python 的新手，想知道哪种方法更“django”？哪种方法更有效？
I am adding date_added and date_modified fields to a bunch of common models in my current project. I am subclassing models.Model and adding the appropriate fields, but I want to add automated save behavior (i.e: evey time anyone calls MyModel.save(), the date_modified field gets updated. I see two approaches: overriding the save() method or adding a pre_save signal handler in the abstract base class.
class CommonData(models.Model):
date_added = models.DateTimeField(default=datetime.datetime.today,null=False,blank=False)
date_modified = models.DateTimeField(default=datetime.datetime.today,null=True,blank=True)
# register a handler for the pre_save to update date_modified
def pre_save_handler(sender, **kwargs):
date_modified = datetime.datetime.today
def __init__():
pre_save.connect(pre_save_handler, sender=self)
or
class CommonData(models.Model):
date_added = models.DateTimeField(default=datetime.datetime.today,null=False,blank=False)
date_modified = models.DateTimeField(default=datetime.datetime.today,null=True,blank=True)
# overriding save
def save(force_insert=False,force_update=False):
date_modified = datetime.datetime.now
return models.Model.save(force_insert, force_update)
I'm new to Django and Python and wondered which approach was more "django"? Which is more efficient? which is the "right" way to do this?
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由于您是 Django 新手，您可能会发现 Django 命令扩展很有用：
http: //code.google.com/p/django-command-extensions/
...其中方便地包含一个 TimeStampedModel，您可以从中派生模型：
http://code.google.com/p/django-command-extensions/wiki/ModelExtensions
Since you're new to Django, you might find the Django Command Extensions useful:
http://code.google.com/p/django-command-extensions/
... which conveniently includes a TimeStampedModel you can derive your models from:
http://code.google.com/p/django-command-extensions/wiki/ModelExtensions
您是否尝试查看
DateTimeField的auto_now=True和auto_now_add=True？它们会自动执行您需要的操作。否则，保存覆盖和信号处理之间没有真正的区别 - 事实上，pre_save 信号是从 django 模型的 save 方法调用的。文档： http://docs.djangoproject.com/en/dev /ref/models/fields/#datefield
Did you try looking at
DateTimeField'sauto_now=Trueandauto_now_add=True? They do just what you need automatically. Otherwise, there is no real difference between doing save override and signal handling - in fact, pre_save signal is being called from django model's save method.Docs: http://docs.djangoproject.com/en/dev/ref/models/fields/#datefield
您可以在 抽象基类 中定义它们，然后继承于此。这有点像有一个 MixIn 也定义了模型字段。
You can define these in an Abstract Base Class and then inherit from that. It's sort of like having a MixIn that also defines model fields.
请注意，
auto_now_add和auto_now使用pre_save，在bulk_create或update时不起作用。因此，例如，在 MySQL 中，date_added 字段将为“0000-00-00 00:00:00”，并且可能会收到警告：“警告：列“date_added”不能为空”。所以你可以使用 auto_now* 但你应该小心。Note that
auto_now_addandauto_nowusespre_save, which not working whenbulk_createorupdate. Thus in your MySQL, for example, date_added field will be '0000-00-00 00:00:00' and it is possible to get warning: 'Warning: Column 'date_added' cannot be null'. So you can use auto_now* but you should be careful.