Swift_類型選擇

Swift_類型選擇

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//類型選擇
func test() {
    
    class MediaItem {
        
    }
    
    class Movie: MediaItem {
        
    }
    
    class Song: MediaItem {
        
    }
    
    let array = [Song(), Movie()]
    
    //is測試 類型判斷
    for item in array {
        if item is Movie {
            print("Movie構建")
        } else if item is Song {
            print("Song構建")
        }
    }
    
    //as測試 類型轉換
    for item in array {
        if let movie = item as? Movie {
            print("可轉換爲Movie: '\(movie)'")
        } else if let song = item as? Song {
            print("可轉換爲Song: '\(song)'")
        }
    }
    
    //AnyObject能夠是任何類型的一個實例 值類型或引用類型
    let someObjects: [AnyObject] = [Movie(), 1 as AnyObject, "33" as AnyObject]
    print(someObjects)
    
    //Any任何類型數據 還能夠是函數 閉包等
    var things = [Any]()
    things.append(0) //值類型
    things.append(Movie()) //引用類型
    things.append({ (name: String) -> String in "Hello, \(name)" }) // 閉包
}