如何在MPMediaItem中使用enumerateValues(forProperties:using :)方法(Swift 3)
问题描述:
我试图接收Now Playing项目的属性数目。 每苹果文档:如何在MPMediaItem中使用enumerateValues(forProperties:using :)方法(Swift 3)
每当应用程序访问一个以上的财产,列举了一组属性键的比取每一个人财产更有效。
于是,我就用自己的方法:
func enumerateValues(forProperties properties: Set<String>,
using block: @escaping (String, Any, UnsafeMutablePointer<ObjCBool>) -> Void)
但我就是不明白应该如何使用。
我的代码:
//MARK: Properties
var allProperties: [String: Any]
var albumTitle: String?
var albumArtist: String?
var title: String?
var artist: String?
var artwork: UIImage?
var genre: String?
var lyrics: String?
var releaseDate: Date?
var playbackDuration: TimeInterval?
var rating: Int?
var assetURL: URL?
var isExplicitItem: Bool?
var isCloudItem: Bool?
var hasProtectedAsset: Bool?
let propertiesSet: Set<String> = [MPMediaItemPropertyAlbumTitle,
MPMediaItemPropertyAlbumArtist,
MPMediaItemPropertyTitle,
MPMediaItemPropertyArtist,
MPMediaItemPropertyArtwork,
MPMediaItemPropertyGenre,
MPMediaItemPropertyLyrics,
MPMediaItemPropertyReleaseDate,
MPMediaItemPropertyPlaybackDuration,
MPMediaItemPropertyRating,
MPMediaItemPropertyAssetURL,
MPMediaItemPropertyIsExplicit,
MPMediaItemPropertyIsCloudItem,
MPMediaItemPropertyHasProtectedAsset]
func getAllMetadata() {
allProperties = nowPlaying?.enumerateValues(forProperties: propertiesSet,
using: //No idea what to put here
-> [String: Any])
}
如何正确使用它?
答
最后我想出了如何使用它。所以我重新写我的功能如下:
func getAllMetadata() {
var allProperties: [String: Any] = [:]
nowPlaying?.enumerateValues(forProperties: propertiesSet, using: {key,value,_ in allProperties[key] = value})
albumTitle = allProperties["albumTitle"] as? String
//and so on
}
本文档可以帮助我了解如何正确使用 - https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Closures.html