iOS - Warning: Attempt to present on whose view is not in the window hierarchy!解决方案

在一个block中进行了present vc的行为，结果present失败，出现了warning：

Warning: Attempt to present on whose view is not in the window hierarchy！

在多方查找验证之后，发现下边方案可以解决此问题：

将之前present的语句换成下边的语句

UIViewController *mviewController = [UIApplication sharedApplication].keyWindow.rootViewController;
                    if (mviewController.presentedViewController) {
                        [mviewController.presentedViewController dismissViewControllerAnimated:false completion:^{
                            [mviewController presentViewController:nav animated:YES completion:nil];
                        }];
                    }else {
                        [mviewController presentViewController:nav animated:YES completion:nil];
                    }

其中的nav时之前创建好的用于present的UINavigationController实例

希望对你有用～