在Django中:Django:为什么_Cached_user是请求的实例属性,而LazyUser是请求的类属性?
def get_user(request):
from django.contrib.auth.models import AnonymousUser
try:
user_id = request.session[SESSION_KEY]
backend_path = request.session[BACKEND_SESSION_KEY]
backend = load_backend(backend_path)
user = backend.get_user(user_id) or AnonymousUser()
except KeyError:
user = AnonymousUser()
return user
class LazyUser(object):
def __get__(self, request, obj_type=None):
if not hasattr(request, '_cached_user'):
from django.contrib.auth import get_user
request._cached_user = get_user(request)
return request._cached_user
class AuthenticationMiddleware(object):
def process_request(self, request):
assert hasattr(request, 'session'), "The Django authentication ..."
request.__class__.user = LazyUser()
return None
正如你可以看到_cached_user
是request
实例的属性,而LazyUser()是类要求的属性:
request.__class__.user = LazyUser()
为什么不同? LazyUser
基本上只是检查是否存在_cached_user
,如果不存在,则查询用户的session
后端。在这种情况下,LazyUser
和_cached_user
不应该是实例request
的属性吗?