What is `@propertyWrapper` and how do you create one?

URLCache stores responses from network requests in memory and/or on disk.
UITableView reuses cell objects as they scroll off screen rather than creating new ones, keeping memory usage constant regardless of how many rows exist.
A property wrapper adds custom logic around getting and setting a property.
| Problem | Cause | Fix | |---------|-------|-----| | #if SIT always falls through to #else | Flag added to Other Swift Flags instead of Active Compilation Conditions | Move flag to the correct…

Answer: A property wrapper adds custom logic around getting and setting a property. SwiftUI's @State, @Binding, and @Published are all property wrappers.

Code Example:

@propertyWrapper
struct Clamped {
    private var value: Int
    let range: ClosedRange<Int>

    var wrappedValue: Int {
        get { value }
        set { value = min(max(newValue, range.lowerBound), range.upperBound) }
    }

    init(wrappedValue: Int, _ range: ClosedRange<Int>) {
        self.range = range
        self.value = min(max(wrappedValue, range.lowerBound), range.upperBound)
    }
}

struct Player {
    @Clamped(0...100) var health: Int = 100
}

var player = Player()
player.health = 150  // clamped to 100
player.health = -10  // clamped to 0