NEW: Learn to build the incredible iOS 15 Weather app today! >>

Why is optional chaining so important?

Paul Hudson    @twostraws   

Updated for Xcode 13.2

Swift’s optional chaining lets us dig through several layers of optionals in a single line of code, and if any one of those layers is nil then the whole line becomes nil.

As a simple example, we might have a list of names and want to find where they should be placed based on the first letter of their surname:

let names = ["Vincent": "van Gogh", "Pablo": "Picasso", "Claude": "Monet"]
let surnameLetter = names["Vincent"]?.first?.uppercased()

There we use optional chaining with the dictionary value because names["Vincent"] might not exist, and again when reading the first character from the surname, because it’s possible the string could be empty.

Optional chaining makes for a very good companion to nil coalescing, because it allows you to dig through layers of optionals while also providing a sensible fall back if any of the optionals are nil.

Returning to our surname example, we could automatically return “?” if we were unable to read the first letter of someone’s surname:

let surnameLetter = names["Vincent"]?.first?.uppercased() ?? "?"

For more information on optional chaining, I can recommend this blog post from Andy Bargh:

Hacking with Swift is sponsored by Essential Developer

SPONSORED Learn the most up-to-date techniques and strategies for testing new and legacy Swift code in this free practical course for iOS devs who want to become complete Senior iOS Developers.

Learn more

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

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: 5.0/5

Unknown user

You are not logged in

Log in or create account

Link copied to your pasteboard.