对基于Django Class Based View的success_url的反向抱怨循环导入

Question

当使用基于方法的视图时,重定向reverse并没有抱怨这个,仍然可以找到根URL配置.但是,在基于类的视图中,它抱怨:

ImproperlyConfigured at /blog/new-post/

The included urlconf 'blog.urls' does not appear to have any
patterns in it. If you see valid patterns in the file then the
issue is probably caused by a circular import.

我的课程定义如下:

class BlogCreateView(generic.CreateView):
    form_class = Blog
    template_name = 'blog/new-post.html'
    success_url = reverse('blog:list-post')

如何正确地使用reverse了success_url基于类的看法？谢谢.

PS:我感兴趣的是为什么runserver在这个错误之后需要重新启动(不像是一个TemplateDoesNotExists不需要重启的错误runserver)

Answer 1

reverse在您的方法中使用是因为reverse在运行视图时调用.

def my_view(request):
    url = reverse('blog:list-post')
    ...

如果你覆盖get_success_url,那么你仍然可以使用reverse,因为在运行视图时get_success_url调用reverse.

class BlogCreateView(generic.CreateView):
    ...
    def get_success_url(self):
        return reverse('blog:list-post')

但是,你不能使用reverse与success_url,因为那时reverse已经加载的URL之前,当模块导入叫.

覆盖get_success_url是一种选择,但最简单的解决方法是使用reverse_lazy而不是反向.

from django.urls import reverse_lazy
# from django.core.urlresolvers import reverse_lazy  # old import for Django < 1.10

class BlogCreateView(generic.CreateView):
    ...
    success_url = reverse_lazy('blog:list-post')

要回答关于重新启动runserver的最后一个问题,ImproperlyConfigured错误与TemplateDoesNotExists加载Django应用程序时发生的错误不同.

Answer 2

尝试使用reverse_lazy而不是reverse在您的CBV中.它是一个懒惰的评估版本reverse.在需要该值之前,它不会执行.

from django.core.urlresolvers import reverse_lazy

class BlogCreateView(generic.CreateView):
    form_class = Blog
    template_name = 'blog/new-post.html'
    success_url = reverse_lazy('blog:list-post')