You have lots of options in this space. For example:
You could create your own project template and use that for your new projects
You could put your core code into a framework and have each app invoke that
You could include the same source code in multiple projects
The best approach really depends on your specific requirements, like what source code control system you use, whether you need to share source code between different organisations, and so on.
Share and Enjoy
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware
let myEmail = "eskimo" + "1" + "@apple.com"