你绝对可以使用是在开关块。请参阅Swift编程语言中的“Type Casting for Any和AnyObject”(尽管它不限于任何当然)。他们有一个广泛的例子：
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")
}
}
