NEW: My new book Pro SwiftUI is out now – level up your SwiftUI skills today! >>

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"]
Hacking with Swift is sponsored by MadMachine

SPONSORED Want to try Swift on microcontrollers? MadMachine provides ways to interact with the physical world in a Swift way. Join us and have fun!

Get it now

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

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.