A peek behind the curtains: Protocols

Even though there are a dozen different numeric types, they are pretty easy to understand and use. This is because they all roughly support the same operations. In other words, once you know how to use an Int, using any one of the flavors is very straight-forward.

One of the truly great features of Swift is how it formalizes the idea of type commonality using what are called protocols. By learning a protocol you instantly understand how an entire family of types that use that protocol work.

In the case of integers, the functionality can be diagrammed like so:

The arrows indicate conformance to (sometimes called adoption of) a protocol. While this graph does not show all of the protocols that integer types conform to, it gives you insight about how things are organized.

Swift is the first protocol-based language. As you begin to understand the protocols that underly the types, you can start leveraging the system in ways not possible with other languages. By the end of this book you will be hooking into existing protocols and even creating new ones of your own.