BLACK FRIDAY: Save 50% on my Swift books and videos! >>

What is an enum?

Paul Hudson       @twostraws

“Enum” is short for “enumeration”, and it’s a way of letting you use fixed names for special values rather than relying on strings or integers.

For example, if we wanted to track how happy a user was, you could use a number scale where -1 meant unhappy, +1 meant happy, and 0 meant they were in between, but then the onus is on you to remember what those numbers mean. A better idea is to use an enum like this one:

enum Satisfaction {
    case unhappy
    case meh
    case happy
}

Those cases can now be referenced as Satisfaction.happy, so it’s clear what you mean – and internally it’s treated no different from an integer, so it has no performance impact.

We can create a Person struct using that new enum, like this:

struct Person {
    var name: String
    var satisfaction: Satisfaction
}

Because Swift knows the satisfaction property must be a value from the Satisfaction enum we can just specify the case we want to use when creating a value:

let person = Person(name: "Taylor", satisfaction: .happy)

Available from iOS 8.0

Did this solution work for you? Please pass it on!

Other people are reading…

About the Swift Knowledge Base

This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.

Download for free!

Want a free 75-minute video teaching functional programming, protocol-oriented programming, and more? This is your lucky day!

MASTER SWIFT NOW
Buy Testing Swift Buy Practical iOS 12 Buy Pro Swift Buy Swift Design Patterns Buy Swift Coding Challenges Buy Server-Side Swift (Vapor Edition) Buy Server-Side Swift (Kitura Edition) Buy Hacking with macOS Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with Swift Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Beyond Code

Was this page useful? Let me know!

Click here to visit the Hacking with Swift store >>