Interoperability between Swift and Objective-C

Swift has been designed to be interoperable with Objective-C. You are able to use Swift APIs in your Objective-C projects, and Objective-C APIs in your Swift projects. Apple has greatly expanded the interoperability between the two languages since Swift was originally released; there are still certain features and functionalities that are not compatible with the new languages.

Even if you're new to iOS or macOS development and have never worked with Objective-C before, and do not intend to, you should still familiarize yourself with this section. There are so many existing Objective-C frameworks and class libraries that you're bound to have to deal with interoperability at some point in time.

We will not cover all of the specific areas of interoperability between the two languages in this book, there are other great books that have been published that focus on only core Swift language features that cover them in great detail...