python - 子类化时出现奇怪的问题？

Question

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'

Answer 1

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。