WWDC23 SALE: Save 50% on all my Swift books and bundles! >>

Dictionary default values

If you try to read a value from a dictionary using a key that doesn’t exist, Swift will send you back nil – nothing at all. While this might be what you want, there’s an alternative: we can provide the dictionary with a default value to use if we request a missing key.

To demonstrate this, let’s create a dictionary of favorite ice creams for two people:

let favoriteIceCream = [
    "Paul": "Chocolate",
    "Sophie": "Vanilla"
]

We can read Paul’s favorite ice cream like this:

favoriteIceCream["Paul"]

But if we tried reading the favorite ice cream for Charlotte, we’d get back nil, meaning that Swift doesn’t have a value for that key:

favoriteIceCream["Charlotte"]

We can fix this by giving the dictionary a default value of “Unknown”, so that when no ice cream is found for Charlotte we get back “Unknown” rather than nil:

favoriteIceCream["Charlotte", default: "Unknown"]
Save 50% in my WWDC23 sale.

SAVE 50% To celebrate WWDC23, all our books and bundles are half price, so you can take your Swift knowledge further without spending big! Get the Swift Power Pack to build your iOS career faster, get the Swift Platform Pack to builds apps for macOS, watchOS, and beyond, or get the Swift Plus Pack to learn advanced design patterns, testing skills, and more.

Save 50% on all our books and bundles!

BUY OUR BOOKS
Buy Pro Swift Buy Pro SwiftUI 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 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 Beyond Code

Was this page useful? Let us know!

Average rating: 4.7/5

 
Unknown user

You are not logged in

Log in or create account
 

Link copied to your pasteboard.