从数据库重新加载django对象

Question

是否可以从数据库刷新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:在跟踪器中找到了重新打开/未修正的战争:http://code.djangoproject.com/ticket/901 .还是不明白为什么维护者不喜欢这个.

Answer 1

从Django 1.8开始,内置刷新对象.链接到文档.

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)

Answer 2

我发现从数据库重新加载对象比较容易:

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

Answer 3

在参考@ grep的评论时,不应该这样做:

# 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

Answer 4

正如@Flimm指出的，这是一个非常棒的解决方案：

foo.refresh_from_db()

这会将所有数据从数据库重新加载到对象中。