让我们有一个代表 Django Controller 的类,其中一个方法名为 _onSuccess
:
class ConfirmController(object):
...
def _onSuccess(self, controller):
...
该类稍后实例化为:
def credit_confirm_info(request, payment_module, template='/some/template.html'):
controller = ConfirmController(request, payment_module)
controller.confirm() # this method calls self._onSuccess
return controller.response
credit_confirm_info = never_cache(credit_confirm_info)
我正在尝试使用ConfirmController的子类:
class ConfirmControllerEx(ConfirmController):
def _onSuccess(self, controller):
# shortened to demonstrate even simple call to super
# causes a different behaviour
super(ConfirmControllerEx, self)._onSuccess(controller)
我可能错过了Python学习中的一些东西,但是有人可以解释为什么上面的子类_onSuccess
与原始方法不等效吗?
如果我确实使用上面的子类ConfirmControllerEx
:
def credit_confirm_info(request, payment_module, template='/some/template.html'):
controller = ConfirmControllerEx(request, payment_module)
controller.confirm() # this method calls self._onSuccess
return controller.response
credit_confirm_info = never_cache(credit_confirm_info)
我收到 NoneType has no method has_header
错误,例如再次调用 credit_confirm_info
但 request
参数等于 None
.
我希望子类和子类方法 _onSuccess
以及对 super
的简单调用不会与原始方法不同。我在这里错过了什么吗?
更新(异常回溯):
Traceback:
File "/home/dunric/Projects/Example.com/satchmo/lib/python2.7/site-packages/django/core/handlers/base.py" in get_response
111. response = callback(request, *callback_args, **callback_kwargs)
File "/home/dunric/Projects/Example.com/satchmo/gastroceny_cz/localsite/views.py" in cod_confirm_info
279. template='shop/checkout/cod/confirm.html')
File "/home/dunric/Projects/Example.com/satchmo/lib/python2.7/site-packages/django/views/decorators/cache.py" in _wrapped_view_func
90. add_never_cache_headers(response)
File "/home/dunric/Projects/Example.com/satchmo/lib/python2.7/site-packages/django/utils/cache.py" in add_never_cache_headers
129. patch_response_headers(response, cache_timeout=-1)
File "/home/dunric/Projects/Example.com/satchmo/lib/python2.7/site-packages/django/utils/cache.py" in patch_response_headers
119. if not response.has_header('Last-Modified'):
Exception Type: AttributeError at /checkout/cod/confirm/
Exception Value: 'NoneType' object has no attribute 'has_header'
最佳答案
我不了解这里涉及的 django 细节,但这个方法:
def _onSuccess(self, controller):
# shortened to demonstrate even simple call to super
# causes a different behaviour
super(ConfirmControllerEx, self)._onSuccess(controller)
不等于父类的_onSuccess
。它通过super
调用父实现,但它忽略调用返回的任何内容,只返回None
(隐式地,通过执行到达方法定义)。鉴于您稍后收到一个错误,似乎表明您有一个 None
对象(NoneType
的实例),其中需要其他内容,这将是我对错误的猜测。但是,如果 _onSuccess
方法的约定始终返回 None
,情况就不是这样了。
关于python - 子类化时出现奇怪的问题?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/21070374/