iOS swift中取枚举类型原始值的方法

enum Planet: Int {    case Mercury = 1, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune}

取swift枚举结构的原始值用toRaw

let earthsOrder = Planet.Earth.toRaw()// earthsOrder is 3

从原始值范围枚举类型用fromRaw

let possiblePlanet = Planet.fromRaw(7)// possiblePlanet is of type Planet? and equals Planet.Uranus

mark:定义枚举类型的时候要把枚举的类型要明确写出，上例中类型是Int