swift2 类型转换
发布时间:2020-12-14 01:59:47 所属栏目:百科 来源:网络整理
导读:class MediaItem { var name: String init(name: String) { self.name = name }}class Movie: MediaItem { var director: String init(name: String,director: String) { self.director = director super.init(name: name) }}class Song: MediaItem { var ar
class MediaItem { var name: String init(name: String) { self.name = name } } class Movie: MediaItem { var director: String init(name: String,director: String) { self.director = director super.init(name: name) } } class Song: MediaItem { var artist: String init(name: String,artist: String) { self.artist = artist super.init(name: name) } } let library = [ Movie(name: "Casablanca",director: "Michael Curtiz"),Song(name: "Blue Suede Shoes",artist: "Elvis Presley"),Movie(name: "Citizen Kane",director: "Orson Welles"),Song(name: "The One And Only",artist: "Chesney Hawkes"),Song(name: "Never Gonna Give You Up",artist: "Rick Astley") ] // the type of "library" is inferred to be [MediaItem]
检查类型var movieCount = 0 var songCount = 0 for item in library { if item is Movie { ++movieCount } else if item is Song { ++songCount } } print("Media library contains (movieCount) movies and (songCount) songs") // prints "Media library contains 2 movies and 3 songs" 向下转型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)") } } // Movie: 'Casablanca',dir. Michael Curtiz // Song: 'Blue Suede Shoes',by Elvis Presley // Movie: 'Citizen Kane',dir. Orson Welles // Song: 'The One And Only',by Chesney Hawkes // Song: 'Never Gonna Give You Up',by Rick Astley Any与AnyObject类型转换let someObjects: [AnyObject] = [ Movie(name: "2001: A Space Odyssey",director: "Stanley Kubrick"),Movie(name: "Moon",director: "Duncan Jones"),Movie(name: "Alien",director: "Ridley Scott") ] for object in someObjects { let movie = object as! Movie print("Movie: '(movie.name)',dir. (movie.director)") } // Movie: '2001: A Space Odyssey',dir. Stanley Kubrick // Movie: 'Moon',dir. Duncan Jones // Movie: 'Alien',dir. Ridley Scott for movie in someObjects as! [Movie] { print("Movie: '(movie.name)',dir. Ridley Scott var things = [Any]() things.append(0) things.append(0.0) things.append(42) things.append(3.14159) things.append("hello") things.append((3.0,5.0)) things.append(Movie(name: "Ghostbusters",director: "Ivan Reitman")) things.append({ (name: String) -> String in "Hello,(name)" }) for thing in things { switch thing { case 0 as Int: print("zero as an Int") case 0 as Double: print("zero as a Double") case let someInt as Int: print("an integer value of (someInt)") case let someDouble as Double where someDouble > 0: print("a positive double value of (someDouble)") case is Double: print("some other double value that I don't want to print") case let someString as String: print("a string value of "(someString)"") case let (x,y) as (Double,Double): print("an (x,y) point at (x),(y)") case let movie as Movie: print("a movie called '(movie.name)',dir. (movie.director)") case let stringConverter as String -> String: print(stringConverter("Michael")) default: print("something else") } } // zero as an Int // zero as a Double // an integer value of 42 // a positive double value of 3.14159 // a string value of "hello" // an (x,y) point at 3.0,5.0 // a movie called 'Ghostbusters',dir. Ivan Reitman // Hello,Michael (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |