How to use Associated Object in Swift

gistfile1.swift

import Foundation

class ABC {}

let abc = ABC()

// in-out expression can be used for CConstVoidPointer parameter.
var key: Void?
objc_setAssociatedObject(abc, &key, "value", UInt(OBJC_ASSOCIATION_RETAIN_NONATOMIC))

println(objc_getAssociatedObject(abc, &key)) // value

Instead of

UInt(OBJC_ASSOCIATION_RETAIN_NONATOMIC)

that would be a better fit

objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN_NONATOMIC