Try It Yourself - SyntaxStudy Editor

HTML / CSS / JS

class BankAccount {
    private var _balance: Double = 0

// Computed property with get/set
    var balance: Double {
        get { _balance }
        set {
            guard newValue >= 0 else { return }
            _balance = newValue
        }
    }

// Property observer
    var owner: String = "" {
        willSet { print("Changing owner from \(owner) to \(newValue)") }
        didSet  { print("Owner changed from \(oldValue) to \(owner)") }
    }

// Lazy property
    lazy var report: String = {
        "Account for \(owner): $\(balance)"
    }()

func deposit(_ amount: Double) {
        guard amount > 0 else { return }
        _balance += amount
    }
}

// Property wrapper
@propertyWrapper
struct Clamped<T: Comparable> {
    var value: T
    let range: ClosedRange<T>

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

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

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

var player = Player()
player.health = 150
print(player.health)  // 100