Xcode7.2.1 Error: Application windows is expected to having a root view controller at the end of the application launch

Cause: This error can occur on newer xcod. In the previous version of IOS5, when the application was loaded, a root view controller was required, and the version below IOS5 would have MainWindow as the boot file, iOS5 later versions did not. A root view controller needs to be created manually.

Add the following code:

Self.window.rootViewController = [[Uiviewcontroller alloc]init];

Xcode7.2.1 Error: Application windows is expected to having a root view controller at the end of the application launch