iOS每次启动都提示：Application windows are expected to have a root view controller at the end of application

运行一次iOS项目，每次启动虽然显示Successed，但控制台都提示：Application windows are expected to have a root view controller at the end of application launch，该怎么解决？

Xcode7.0 只需在AppDelegate.m的didFinishLaunchingWithOptions添加如下一行代码即可：

self.window.rootViewController = [[UIViewController alloc]init];

这个问题是我在学习《IOS编程》第4章创建Hypnosister项目时遇到的，该书在编写的时候基于Xcode5，作者就没有提到这个问题。