Swift_类型选择

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//类型选择

func test() {

    class MediaItem {

    }

    class Movie: MediaItem {

    }

    class Song: MediaItem {

    }

    let array = [Song(), Movie()]

    //is测试 类型判断

    for item in array {

        if item is Movie {

            print("Movie构建")

        } else if item is Song {

            print("Song构建")

        }

    }

    //as测试 类型转换

    for item in array {

        if let movie = item as? Movie {

            print("可转换为Movie: '\(movie)'")

        } else if let song = item as? Song {

            print("可转换为Song: '\(song)'")

        }

    }

    //AnyObject可以是任何类型的一个实例 值类型或引用类型

    let someObjects: [AnyObject] = [Movie(), 1 as AnyObject, "33" as AnyObject]

    print(someObjects)

    //Any任何类型数据 还可以是函数 闭包等

    var things = [Any]()

    things.append(0) //值类型

    things.append(Movie()) //引用类型

    things.append({ (name: String) -> String in "Hello, \(name)" }) // 闭包

}