Swift - in-place mutation

playground.swift

func address(o: UnsafeRawPointer) -> Int {
    return Int(bitPattern: o)
}

func addressHeap<T: AnyObject>(o: T) -> Int {
    return unsafeBitCast(o, to: Int.self)
}

////////////////////////////////////////////

struct Point {
    var x: Float
    var y: Float
}

struct Size {
    var width: Float
    var height: Float
}

struct Rect {
    let origin: Point
    var size: Size
}

////////////////////////////////////////////

var frame = Rect(origin: Point(x: 0, y: 0), size: Size(width: 10, height: 10)) {
    didSet {
        print("Frame changed! \(frame)")
    }
}

print(address(o: &frame.size))

frame.size.height = 600

print(address(o: &frame.size))

//Should print the same address twice, before and after changing height