ios – Swift的编码/解码枚举(Xcode 6.1)

var priority : Priority! = Priority.defaultPriority

func encodeWithCoder(aCoder: NSCoder) {
        aCoder.encodeInteger(priority.toRaw(),forKey: "priority") //toRaw may not yield the result I am expecTing
    }

    required init(coder aDecoder: NSCoder) {
        priority = aDecoder.decodeIntegerForKey("priority") //complaining about conflicTing types
    }

枚举如下：

enum Priority : Int {
        case defaultPriority = 0
        case lowPriority = 1
        case mediumPriority = 2
        case highPriority = 3
    }

编码/解码这个的最佳方法是什么？