从数据库重新加载Django对象

是否可以从数据库中刷新Django对象的状态？我的意思是行为大致相当于：

new_self = self.__class__.objects.get(pk=self.pk)
for each field of the record:
setattr(self, field, getattr(new_self, field))

更新：在跟踪器中发现重新打开/WontFix WAR：http：//code.djangoproject.com/ticket/901。我还是不明白为什么维护人员不喜欢这样。

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小开

I've found it relatively easy to reload the object from the database like so:

x = X.objects.get(id=x.id)

小开

In reference to @grep's comment, shouldn't it be possible to do:

# Put this on your base model (or monkey patch it onto django's Model if that's your thing)
def reload(self):
new_self = self.__class__.objects.get(pk=self.pk)
# You may want to clear out the old dict first or perform a selective merge
self.__dict__.update(new_self.__dict__)


# Use it like this
bar.foo = foo
assert bar.foo.pk is None
foo.save()
foo.reload()
assert bar.foo is foo and bar.foo.pk is not None

小开

最佳答案

As of Django 1.8 refreshing objects is built in. Link to docs.

def test_update_result(self):
obj = MyModel.objects.create(val=1)
MyModel.objects.filter(pk=obj.pk).update(val=F('val') + 1)
# At this point obj.val is still 1, but the value in the database
# was updated to 2. The object's updated value needs to be reloaded
# from the database.
obj.refresh_from_db()
self.assertEqual(obj.val, 2)

小开

As @Flimm pointed out, this is a really awesome solution:

foo.refresh_from_db()

This reloads all data from the database into the object.