使用UIAlertController报错

if (IOS8) {
        UIAlertController * deleAlert = [UIAlertController alertControllerWithTitle:nil message:@"是否删除?" preferredStyle:UIAlertControllerStyleAlert];
        [self.view.window.rootViewController presentViewController:deleAlert animated:YES completion:nil];
        UIAlertAction * sureAction = [UIAlertAction actionWithTitle:@"是" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
  
        }];
        UIAlertAction * cancelAction = [UIAlertAction actionWithTitle:@"否" style:UIAlertActionStyleCancel handler:nil];
        [deleAlert addAction:sureAction];
        [deleAlert addAction:cancelAction];
    }

[self.view.window.rootViewController presentViewController:deleAlert animated:YES completion:nil];

如果使用

[self presentViewController:deleAlert animated:YES completion:nil];

会报错：

Presenting view controllers on detached view controllers is discouraged