UIAlertController

• 继iOS8以后，以UIAlertController代替了UIAlertView，具体使用方法如下：

//定义一个UIAlertController
UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"警告！" message:@"是否要注销？" preferredStyle:UIAlertControllerStyleActionSheet];
//定义UIAlertAction对象，包括文字，类型和要实现的方法
UIAlertAction *no = [UIAlertAction actionWithTitle:@"否" style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
}];
UIAlertAction *yes = [UIAlertAction actionWithTitle:@"是" style:UIAlertActionStyleDestructive handler:^(UIAlertAction * _Nonnull action) {
[self.navigationController popViewControllerAnimated:YES];
}];
//将定义的UIAlertAction添加到UIAlertController中
[alert addAction:no];
[alert addAction:yes];
//使用该方法才能将UIAlertController显示出来
[self presentViewController:alert animated:YES completion:nil];