[swift] 14. 타입 캐스팅(Type Casting)

is 

특정 타입인지 확인

if val is Class {
	// Do
}

as, as?

for item in library {
    if let movie = item as? Movie {
        print("Movie: \(movie.name), dir. \(movie.director)")
    } else if let song = item as? Song {
        print("Song: \(song.name), by \(song.artist)")
    }
}

Any, AnyObject