Apple announced today its plan to bring UIKit to Mac. This is a project that has several years of development behind it. Apple is now testing the new multi-platform frameworks with its own stock applications in macOS Mojave. It will be available to third-party developers in 2019.
Apple wants to bring iOS applications from UIKit to Mac
Apple is expanding the iOS interface frames to work well on the Mac window system. Specifically, he said he would not merge iOS and macOS.
This UI is being tested internally by Apple this year, and developers will learn how to start using it in their applications next year. UIKit on a Mac will support mouse and trackpad input, window resizing, copy and paste, drag and drop, and everything else needed to make a native Mac application feel like a native Mac application.
It is not clear whether Apple will have development sessions on this initiative, as most of the details are constantly changing as the Mac UIKit will not be released until 2019.