django - django.shortcuts reverse() 在类 var 结果中调用错误 URLconf 'xxx.urls' 似乎没有任何模式

Question

1.evn

• python3.5
• django2.2

2.问题

• 在初始化类变量时调用 django.shortcut: reverse()，编译完全没问题。
• 出现运行时错误：包含的 URLconf 'xxx.urls' 中似乎没有任何模式。如果您在文件中看到有效模式，则问题可能是由循环导入引起的。
• 此外，此错误消息非常具有误导性，我花了很多时间检查实际上完全正确的 url。

3.代码示例

from django.views import View
from django.shortcuts import render, reverse, redirect

class LoginView(View):

  main_page = reverse('main')   => cause runtime error

  def get(...):

  def post(...):


urlpatterns = [
    path(r'login/', authviews.LoginView.as_view(), name='login'),
    path(r'main/', authviews.MainView.as_view(), name='main'),
    ...

4.运行时错误信息

File ".../auth/view/views.py", line 10, in <module>
  class LoginView(View):
File ".../auth/view/views.py", line 13, in LoginView
  main_page = reverse('main')
File ".../.local/lib/python3.5/site-packages/django/urls/base.py", line 90, in reverse
  return iri_to_uri(resolver._reverse_with_prefix(view, prefix, *args, **kwargs))
File ".../.local/lib/python3.5/site-packages/django/urls/resolvers.py", line 600, in _reverse_with_prefix
  self._populate()
File ".../.local/lib/python3.5/site-packages/django/urls/resolvers.py", line 438, in _populate
  for url_pattern in reversed(self.url_patterns):
File ".../.local/lib/python3.5/site-packages/django/utils/functional.py", line 80, in __get__
  res = instance.__dict__[self.name] = self.func(instance)
File ".../.local/lib/python3.5/site-packages/django/urls/resolvers.py", line 580, in url_patterns
  raise ImproperlyConfigured(msg.format(name=self.urlconf_name))
django.core.exceptions.ImproperlyConfigured: The included URLconf 'xxx.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.

5.分析

• 在 class_view 中调用“reverse()”时，可能尚未加载 url

6.分辨率

• way1：使用 django.urls.reverse_lazy() 代替 => 建议方式
• 方式2：将“reverse('main')”调用移动到 get() 或 post()

7.建议

• 最好将运行时错误消息细化为更准确

标签： djangoreverse