Xcode version 6.1.1 creates a new IOS – “Application -” single view application. In addition to the appdelegate file, there is also the viewcontroller automatically established by the system. Later, I changed the name of the viewcontroller and ran an error unknown class viewcontroller in interface builder file

Solution:

Reddit found:

It seems like you have set a custom class named “Descript” for your viewcontroller in the storyboard by accident.Select the viewcontroller in the storyboard and go to Identity Inspector and check whats set as custom class there.

Here, I open the main.storyboard file, select the home view controller, and on the custom class item in the identity inspector on the right, modify the class to my renamed file (in fact, I just need to modify it to an existing viewcontroller)