Django 类视图：在调度中验证对象

Question

有没有一种已经确定的方法，可以在调度时验证一个对象，而不需要在后面调用self.get_object()时再额外去数据库查询一次？

这是我目前的做法（为了这个问题稍微修改了一下）：

class CourseUpdateView(UpdateView):
    def dispatch(self, request, *args, **kwargs):

        self.request = request
        self.kwargs = kwargs
        self.object = self.get_object()

        if self.object.is_online:
            messages.warning(request, "Sorry this one can't be updated")
            return redirect("course:detail", pk=self.kwargs['pk'])

        # this is going to call self.get_object again isn't it?
        return UpdateView.dispatch(self, request, *args, **kwargs)

Answer 1

你可以把get_object()这个函数的结果缓存起来。

下面是一个简单的例子：

class CourseUpdateView(UpdateView):
    # [...] your dispatch method

    def get_object(self):
        # it doesn't matter how many times get_object is called per request
        # it should not do more than one request
        if not hasattr(self, '_object'):
            self._object = super(CourseUpdateView, self).get_object()
        return self._object