Swift Programming: The Big Nerd Ranch Guide, 3rd Edition

Chapter 25. Equatable, Comparable, and Hashable

You have spent a lot of time now learning to model data. You have explored value types and reference types and the “free” features that you can sometimes get from them, such as compiler-synthesized empty initializers.

You have also seen useful behaviors that are enabled for you when you conform to certain protocols from the Swift standard library. For example, conforming to CustomStringConvertible and implementing its required description property lets you customize how instances of your types will print to the console. Conforming to Error allows instances of your types to be thrown as errors from functions that do failable work.

There are other common behaviors that you can unlock by conforming ...