Day 2: Property Wrappers

What does this print?

@propertyWrapper
struct Cap {
  private var n = 0
  var wrappedValue: Int {
    get { n }
    set { n = min(newValue, 9) }
  }
}
struct Box { @Cap var v: Int }

var b = Box()
b.v = 12
print(b.v)

Try it in the online Swift Playground →

[spoiler title="Solution"]

Answer:

9

Explanation:

The wrapper caps assigned values at 9, so setting 12 stores 9.

[/spoiler]

Further Reading

• Generics, Protocols & Functional Programming in Swift
• Object-Oriented Programming Beyond the Basics