LifeJourney

We only live once.

Understanding Swift Copy-on-Write mechanisms

	final class Ref<T> {
	var val: T
	init(_ v: T) {val = v}
	}

	struct Box<T> {
	var ref: Ref<T>
	init(_ x: T) { ref = Ref(x) }

	var value: T {
	get { return ref.val }
	set {
	if !isKnownUniquelyReferenced(&ref) {
	ref = Ref(newValue)
	return
	}
	ref.val = newValue
	}
	}
	}

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Sample code from official github repo

Kevin Nien