ios - 如何从NSUserDefaults检索数据？

Question

目前，我尝试制作音乐播放列表应用程序。我尝试从NSUserDefaults保存和检索播放列表数据。保存数据时没有问题，但是检索数据时出现错误。

我有:

Terminating app due to uncaught exception 'MPMediaItemCollectionInitException', reason: '-init is not supported, use -initWithItems:

我正在关注 Play iPod playlist retrieved from a saved persistentid list的答案，但我尝试迅速编写它。

这是我的保存功能:

func savePlaylist(var mediaItemCollection: MPMediaItemCollection){

    var items: NSArray = mediaItemCollection.items

    var listToSave: NSMutableArray = NSMutableArray()

    for song in items{

        var persistentId: AnyObject! = song.valueForProperty(MPMediaItemPropertyPersistentID)

        listToSave.addObject(persistentId)

    }

    var data: NSData = NSKeyedArchiver.archivedDataWithRootObject(listToSave)

    NSUserDefaults.standardUserDefaults().setObject(data, forKey: "songsList")
    NSUserDefaults.standardUserDefaults().synchronize()

}

这是我的检索功能:

func setupMusic(){

    if NSUserDefaults.standardUserDefaults().objectForKey("songsList") != nil{

        var theList: NSMutableArray = NSMutableArray()

        var data: NSData = (NSUserDefaults.standardUserDefaults().objectForKey("songsList") as? NSData)!

        var decodedData: NSArray  = (NSKeyedUnarchiver.unarchiveObjectWithData(data) as? NSArray)!

        theList.addObjectsFromArray(decodedData as [AnyObject])

        var allTheSongs: NSMutableArray = NSMutableArray()

        for var i = 0; i < theList.count; i++ {

            var songQuery = MPMediaQuery.songsQuery()

            var songs: NSArray = songQuery.items

            allTheSongs.addObject(songs)

        }

        var currentQueue: MPMediaItemCollection = MPMediaItemCollection()

        myMusicPlayer?.setQueueWithItemCollection(currentQueue)


    }else{
        println("fail!!!!!!!!!!!!")
    }

}

我该如何解决？

Answer 1

这是问题var currentQueue: MPMediaItemCollection = MPMediaItemCollection()
您必须使用项目init
按照苹果的documentation。

init(items:) Designated Initializer

Initializes a media item collection with an array of media items. Declaration

Swift

init!(items items: [AnyObject]!) Parameters items

The array of items you are assigning to the media item collection.

您必须使用以下项进行初始化

var currentQueue: MPMediaItemCollection = MPMediaItemCollection(items:itemsArray)