Kodebits Day 23: Dictionary Defaults

What does this print?

var m = ["a": 4, "b": 6]
print(m["c", default: 8])
m["a", default: 0] += 1
print(m["a"]!)

Try it in the online Swift Playground →

[spoiler title="Solution"]

Answer:

8
5

Explanation:

The `default` parameter provides a fallback value for missing keys. It works for both reading (`m["c", default: 8]` returns 8) and write-through updates.

[/spoiler]

Further Reading

• Applying Protocol-Oriented Programming
• Data Persistence in SwiftUI