Why does Swift need enums?

Paul Hudson @twostraws May 28th 2020

Enums are an extraordinarily powerful feature of Swift, and you’ll see them used in a great many ways and places. Many languages don’t have enums and get by just fine, so you might wonder why Swift needs enums at all!

Well, at their simplest an enum is simply a nice name for a value. We can make an enum called Direction with cases for north, south, east, and west, and refer to those in our code. Sure, we could have used an integer instead, in which case we’d refer to 1, 2, 3, and 4, but could you really remember what 3 meant? And what if you typed 5 by mistake?

So, enums are a way of us saying Direction.north to mean something specific and safe. If we had written Direction.thatWay and no such case existed, Swift would simply refuse to build our code – it doesn’t understand the enum case. Behind the scenes, Swift can store its enum values very simply, so they are much faster to create and store than something like a string.

As you progress, you’ll learn how how Swift lets us add more functionality to enums – they are more powerful in Swift than in any other language I have seen.

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