alert错误：

1、reason: 'UIAlertController:supportedInterfaceOrientations was invoked recursively!'

递归错误，在网上找到了解决方法，但是不知道为什么。
解决方法：
建一个UIAlertController的分类：supportedInterfaceOrientations

// 避免alert递归调用
// bug: reason: 'UIAlertController:supportedInterfaceOrientations was invoked recursively!'
#if __IPHONE_OS_VERSION_MAX_ALLOWED < 90000
- (NSUInteger)supportedInterfaceOrientations{
    return UIInterfaceOrientationMaskPortrait;
}
#else
- (UIInterfaceOrientationMask)supportedInterfaceOrientations {
    return UIInterfaceOrientationMaskPortrait;
}
#endif

参考文章：
http://blog.csdn.net/jiang314/article/details/52402961