UIAlertController的基本使用

UIAlertController* alert = [UIAlertController alertControllerWithTitle:nil message:@"警告"preferredStyle:UIAlertControllerStyleActionSheet];
    
    [alert addAction:[UIAlertAction actionWithTitle:@"返回" style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
        //点击"返回"的回调 Cancel普通返回样式
    }]];
    [alert addAction:[UIAlertAction actionWithTitle:@"确定" style:UIAlertActionStyleDestructive handler:^(UIAlertAction * _Nonnull action)
    {//Destructive 这个样式字体会变红 看起来就和重要选择一样
        
        [self.deals removeObjectAtIndex:0];
        [self.tableView deleteRowsAtIndexPaths:@[[NSIndexPath indexPathForRow:0 inSection:0]] withRowAnimation:UITableViewRowAnimationFade];
    
    }]];
    //UIAlertController添加方法并且有个动画
    [self presentViewController:alert animated:YES completion:nil];

 // 添加文本输入框
    [alert addTextFieldWithConfigurationHandler:^(UITextField *textField) {
        textField.placeholder = @"占位字符串";//placeholder 占位符
    }];