UIAlerView、UIActionSheet 和UIAlertViewController(点击注销确认按钮实现）

 - (IBAction)loginOut:(UIBarButtonItem *)sender {
     UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:@"确定要退出登陆吗" delegate:self cancelButtonTitle:@"取消" destructiveButtonTitle:@"确定退出" otherButtonTitles:nil];
     [actionSheet showInView:self.view];
 }

 -(void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex{
     if (buttonIndex == ) {
         //退出
         [self.navigationController popViewControllerAnimated:YES];
     }
 }

从IOS8之后，UIAlerView和UIActionSheet 两个合并在了一起，使用了一个新的控制器UIAlertViewController，好处就是不用实现代理

UIActionSheetDelegate和UIAlerViewDelegate

UIAlertViewController使用步骤如下：

//第一步，创建控制器
    UIAlertController *alertVC = [UIAlertController alertControllerWithTitle:@"确定退出吗" message:nil preferredStyle:UIAlertControllerStyleActionSheet];
    //第二步，创建按钮
    UIAlertAction *action1 = [UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
        NSLog(@"%s",__func__);
    }];
    UIAlertAction *action2 = [UIAlertAction actionWithTitle:@"确定" style:UIAlertActionStyleDestructive handler:^(UIAlertAction * _Nonnull action) {
        [self.navigationController popViewControllerAnimated:YES];
    }];
    //第三步，添加按钮
    [alertVC addAction:action1];
    [alertVC addAction:action2];
    //第四步，显示弹窗，相当于show操作
    [self presentViewController:alertVC animated:YES completion:nil];