About the Header file
CoreRing.framework can be used in Swift, but it's written in Objective-C.
The features which are provided by this framework are defined in header files which are contained by the SDK package.
By importing CoreRing.h, the app can access all definitions in CoreRing.framework.
This file defines constants and the CRCommon class.
This file defines the CRApplication class and the CRApplicationDelegate class.