In the previous recipe, we learned how to add a new code into an existing Objective-C project. However, you shouldn't only add new code, but also, as far as possible, you should migrate your old code to the new Swift language.
If you would like to keep your application core on Objective-C, that's ok, but remember that the new features are going to be added to Swift, and it will be difficult to keep two languages in the same project.
In this recipe, we are going to port part of the code, which is written in Objective-C to Swift.
Make a copy of the previous recipe. If you are using any version control system, this is a good time to commit your changes. If you are not using a version control system, check Chapter 1, Getting Started with Xcode and Swift, to see how to add it to your project.