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"]

SPONSORED Are you tired of wasting time debugging your Swift app? Instabug’s SDK is here to help you minimize debugging time by providing you with complete device details, network logs, and reproduction steps with every bug report. All data is attached automatically, and it only takes a line of code to setup. Start your free trial now and get 3 months off exclusively for the Hacking with Swift Community.

Start your free trial!

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