UIAlertController警告视图和操作表单

 //创建一个myAlert1操作表单对象(UIAlertControllerStyleActionSheet为操作表单，UIAlertControllerStyleAlert为警告视图)
   UIAlertController *myAlert1 = [UIAlertController alertControllerWithTitle:@"Are you sure?" message:nil preferredStyle:UIAlertControllerStyleActionSheet];
     //创建一个操作表中的按钮对象(警告框、操作表默认没有按钮)
     //参数handler参数是个块，具体实现点击这个按钮所需处理的内容
     UIAlertAction *yesAction = [UIAlertAction actionWithTitle:@"Yes" style:UIAlertActionStyleDestructive handler:^(UIAlertAction *action){

         NSString *msg;
         if ([self.nameText.text length] > ) {
             msg = [NSString stringWithFormat:@"Your name is %@",self.nameText.text];

         }else{
             msg = @"You haven't input";
         }

         UIAlertController *myAlert2 = [UIAlertController alertControllerWithTitle:@"Something Was Done" message:msg preferredStyle:UIAlertControllerStyleAlert];

         UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:@"Phew!" style:UIAlertActionStyleCancel handler:nil];
     //往myAlert2警告框对象中添加这个cancel按钮
         [myAlert2 addAction:cancelAction];
     //在屏幕中绘制警告框对话框
         [self presentViewController:myAlert2 animated:YES completion:nil];
     }];
     UIAlertAction *noAction = [UIAlertAction actionWithTitle:@"No way!" style:UIAlertActionStyleCancel handler:nil];

     [myAlert1 addAction:yesAction];
     [myAlert1 addAction:noAction];

     //------这段代码开发iPhone app时可不写,iPad必须要写-------
     UIPopoverPresentationController *ppc = myAlert1.popoverPresentationController;

     if (ppc != nil) {
         ppc.sourceView = sender;
         ppc.sourceRect = sender.bounds;
         //设置iPad操作表单的属性，使箭头方向为往下指
         ppc.permittedArrowDirections = UIPopoverArrowDirectionDown;
     }
     //------这段代码开发iPhone app时可不写,iPad必须要写-------

     [self presentViewController:myAlert1 animated:YES completion:nil];