ReadOnce

ReadOnce.swift

// I wrote this and then decided its an overengineered piece of bullshit code. Just deleting it makes me sad so let it forever take up space on Github

// a property that flips back to its default value when it is read
// TODO: does this have proper value semantics with the class inside? And do we even care?
@propertyWrapper struct ReadOnce<Value> {
    init(initialValue: Value) {
        defaultValue = initialValue
        box = ValueBox(value: initialValue)
    }
    private let defaultValue: Value
    final class ValueBox {
        init(value: Value) { self.value = value }
        var value: Value
    }
    private var box: ValueBox
    var value: Value {
        get {
            let result = box.value
            box.value = defaultValue
            return result
        }
        set {
            box.value = newValue
        }
    }
}