Presenting view controllers on detached view controllers

在childrenVIewController 中调用
[self presentViewController:controller animated:YES completion:nil];
会报标题中的错；
解决方法：
[self.view.window.rootViewController presentViewController:controller animated:YES completion:nil];
[参考链接:]http://blog.csdn.net/wangzitao126/article/details/41578921