OC报错：Application tried to present modally a view controller <UIAlertController

Application tried to present modally a view controller <UIAlertController: 0x155882a00> that is already being presented by <UINavigationController: 0x154819c00> 这个问题是因为当前控制器A，要弹出控制器B，而控制器B已经被弹出或者正在被弹出的时候又调用了一次

发现 [self presentViewController:alertVc animated:YES completion:nil]; 被调用两次

更改：只保留设置数据完毕后写的[self presentViewController:alertVc animated:YES completion:nil]; 方法

纯属低级错误，实在汗颜