UIAlertController *alert=[UIAlertController alertControllerWithTitle:@"选择信誉度" message:nil preferredStyle:UIAlertControllerStyleActionSheet];
//设置按钮
UIAlertAction *btn2=[UIAlertAction actionWithTitle:@"确定" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
}];
[alert addAction:btn2];
UIAlertAction *btn1=[UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleCancel handler:nil];
//把按钮增加到alert上
[alert addAction:btn1];
//模态弹出
[self presentViewController:alert animated:YES completion:nil];
