FREE TRIAL: Accelerate your app development career with Hacking with Swift+! >>

Sets

Sets are collections of values just like arrays, except they have two differences:

  1. Items aren’t stored in any order; they are stored in what is effectively a random order.
  2. No item can appear twice in a set; all items must be unique.

You can create sets directly from arrays, like this:

let colors = Set(["red", "green", "blue"])

When you look at the value of colors inside the playground output you’ll see it doesn’t match the order we used to create it. It’s not really a random order, it’s just unordered – Swift makes no guarantees about its order. Because they are unordered, you can’t read values from a set using numerical positions like you can with arrays.

If you try to insert a duplicate item into a set, the duplicates get ignored. For example:

let colors2 = Set(["red", "green", "blue", "red", "blue"])

The final colors2 set will still only include red, green, and blue once.

Hacking with Swift is sponsored by Essential Developer

SPONSORED Join a FREE crash course for iOS devs who want to become complete senior developers — from October 18th to 24th. Learn how to apply iOS app architecture patterns through a series of lectures and practical coding sessions.

Learn more

Sponsor Hacking with Swift and reach the world's largest Swift community!

BUY OUR BOOKS
Buy Pro Swift Buy Swift Design Patterns Buy Testing Swift Buy Hacking with iOS Buy Swift Coding Challenges Buy Swift on Sundays Volume One Buy Server-Side Swift (Vapor Edition) Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Advanced iOS Volume Three Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with macOS Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Server-Side Swift (Kitura Edition) Buy Beyond Code

Was this page useful? Let us know!

Average rating: 4.6/5

 
Unknown user

You are not logged in

Log in or create account
 

Link copied to your pasteboard.