Question

基本上，我正在尝试构建一个音乐播放器应用程序，以便学习iOS平台和Swift 3，但我目前只是坚持一个简单的步骤。我正在尝试创建一个类型歌曲的数组，并在歌曲艺术家之后追加该数组的歌曲名称等。

该功能也需要修改。我之前使用过一系列名称，但之后我决定创建这个结构。

import Foundation

struct Song {


    var _songTitle:String?

    var _songArtist:String?

    var _songDuration:Double?

    var _songCover:String?

}


import AVFoundation

类AudioManager：NSObject，AVAudioPlayerDelegate {

static let sharedInstance = AudioManager()

var currentSong = 0

var currentTime = 0

var player: AVAudioPlayer = AVAudioPlayer()

private override init() {}


private var songs: [Song] = []

func play()
{

        player.play()
}

func stop() {
    if player.isPlaying{
     player.stop()
    }

}

func playThis()
{

    do
    {
        guard let audioPath = Bundle.main.path(forResource: songs._songTitle?[currentSong], ofType: ".mp3")
            else {
                return

        }
        try player = AVAudioPlayer(contentsOf: NSURL(fileURLWithPath: audioPath) as URL)

    }
    catch
    {
        print ("ERROR")

    }


}


    func audioPlayerDidFinishPlaying(_ player: AVAudioPlayer, successfully flag: Bool)
{

    if flag {
        currentSong += 1
    }

    if ((currentSong + 1) == songs.count) {
        currentSong = 0
    }


}

func skipForward() {
    var timeToSkip: TimeInterval = player.currentTime
    timeToSkip += 5.0
    player.currentTime = timeToSkip
}

func skipBack() {
    var timeToSkip: TimeInterval = player.currentTime
    timeToSkip -= 5.0
    player.currentTime = timeToSkip
}

func gettingSongNames()
{
    let folderURL = URL(fileURLWithPath:Bundle.main.resourcePath!)

    do
    {
        let songPath = try FileManager.default.contentsOfDirectory(at: folderURL, includingPropertiesForKeys: nil, options: .skipsHiddenFiles)

        //loop through the found urls
        for song in songPath
        {
            var mySong = song.absoluteString

            if mySong.contains(".mp3")
            {
                let findString = mySong.components(separatedBy: "/")
                mySong = findString[findString.count-1]
                mySong = mySong.replacingOccurrences(of: "%20", with: " ")
                mySong = mySong.replacingOccurrences(of: ".mp3", with: "")
                song._songTitle.append(mySong)

            }

        }


    }
    catch
    {
        print ("ERROR")
    }
}

}

Answer 1

您可以在AudioManager类实例中添加一个方法来执行添加歌曲，如下所示：

func addSong(song: Song) {
    songs.append(song)
}

你可以像这样使用它：

let song = Song(_songTitle: "Title", _songArtist: "Artist", _songDuration: 0, _songCover: "Cover")
AudioManager.sharedInstance.addSong(song: song)

你不能song._songTitle.append(mySong)，因为_songTitle是一个字符串，而不是一个数组。如果要进行追加，则必须将其声明为数组。

Answer 2

您正在以错误的顺序组合struct member access和array indexing。例如，您有一个song类型的数组[Song]，这是一组歌曲，并且可以访问您编写的特定标题：

songs._songTitle?[currentSong]

其中说“songs具有数组值属性_songTitle，访问其currentSong元素” - 这是向后的。您需要首先访问数组元素，返回Song，然后返回属性：

songs[currentSong]._songTitle

您似乎也希望创建一个仅指定标题的新歌曲。要做到这一点，你应该在init上添加Song方法：

init(withTitle: String) { ... }

将新歌曲的标题设置为提供的值，将其他属性设置为nil。（如果您不了解init方法，请参阅Apple的Swift书。）

一旦你有了这个初始化器，就会添加一首新歌：

songs.append( Song(withTitle:mySong) )

HTH

结构在另一个类中传递变量

2 个答案: