Swift：在switch语句中测试类类型

for thing in things {
    switch thing {
    case 0 as Int:
        println("zero as an Int")
    case 0 as Double:
        println("zero as a Double")
    case let someInt as Int:
        println("an integer value of (someInt)")
    case let someDouble as Double where someDouble > 0:
        println("a positive double value of (someDouble)")
    case is Double:
        println("some other double value that I don't want to print")
    case let someString as String:
        println("a string value of "(someString)"")
    case let (x,y) as (Double,Double):
        println("an (x,y) point at (x),(y)")
    case let movie as Movie:
        println("a movie called '(movie.name)',dir. (movie.director)")
    default:
        println("something else")
    }
}