UIAlertController——系统类型的使用方法

1. 声明和使用方法（标准的Alert样式）

//UIAlertController风格：UIAlertControllerStyleAlert
  UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"没有标题的标题"
                                                                           message:@"学无止境，漫漫长路"
                                                                    preferredStyle:UIAlertControllerStyleAlert ];

  //添加取消到UIAlertController中
  UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleDefault handler:nil];
  [alertController addAction:cancelAction];

  //添加确定到UIAlertController中
  UIAlertAction *OKAction = [UIAlertAction actionWithTitle:@"确定" style:UIAlertActionStyleDefault handler:nil];
  [alertController addAction:OKAction];

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

2. 声明和使用方法(标准的Alert Sheet样式)

UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"标准的Action Sheet样式"
                                                                           message:nil
                                                                    preferredStyle:UIAlertControllerStyleActionSheet];
  //取消:style:UIAlertActionStyleCancel
  UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleCancel handler:nil];
  [alertController addAction:cancelAction];
  //了解更多:style:UIAlertActionStyleDestructive
  UIAlertAction *moreAction = [UIAlertAction actionWithTitle:@"了解更多" style:UIAlertActionStyleDestructive handler:nil];
  [alertController addAction:moreAction];
  //原来如此:style:UIAlertActionStyleDefault
  UIAlertAction *OKAction = [UIAlertAction actionWithTitle:@"原来如此" style:UIAlertActionStyleDefault handler:nil];
  [alertController addAction:OKAction];

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

3. UIAlertActionStyle三种类型

style:UIAlertActionStyleDefault//对按钮应用标准样式
style:UIAlertActionStyleCancel//对按钮应用取消样式，即取消操作
style:UIAlertActionStyleDestructive//对按钮应用警示性样式，提示用户这样做可能会删除或者改变某些数据