Question

我创建了一个用于向用户显示最新和顶级乡村歌曲的应用程序。我使用Firebase数据库发送和接收歌曲信息。这是在Xcode中使用Swift和UIKit。

我创建了一个名为Song的类，它处理从Firebase获得的所有信息。那个班级在下面。

import Foundation
import UIKit

class Song {

//private var _imageURL: String!
private var _videoURL: NSMutableURLRequest!
private var _songTitle: String!
private var _artistName: String!
private var _cellNum: Int!
private var _lastNum: Int!
private var _spotifyLink: String!
private var _itunesLink: String!
private var _lyrics: String!
private var _saved: Bool!

//    var imageURL: String{
//        return _imageURL
//    }

var videoURL: NSMutableURLRequest{
    return _videoURL
}

var songTitle: String{
    return _songTitle
}

var artistName: String{
    return _artistName
}

var cellNum: Int{
    return _cellNum
}

var lastNum: Int{
    return _lastNum
}

var spotifyLink: String{
    return _spotifyLink
}

var itunesLink: String{
    return _itunesLink
}

var lyrics: String{
    return _lyrics
}

var saved: Bool{
    get{
        return _saved
    }
    set{
        _saved = newValue
    }
}

init(videoURL: NSMutableURLRequest, songTitle: String, artistName: String, cellNum: Int, lastNum: Int, spotifyLink: String, itunesLink: String, lyrics: String, saved: Bool) {

    //_imageURL = imageURL
    _videoURL = videoURL
    _songTitle = songTitle
    _artistName = artistName
    _cellNum = cellNum
    _lastNum = lastNum
    _spotifyLink = spotifyLink
    _itunesLink = itunesLink
    _lyrics = lyrics
    _saved = saved
}
}

在我的一个swift文件中，我初始化了一个类型为Song的新数组，以保存用户保存的信息。

var savedSongs = [Song]()

其中一个故事板中有一个按钮，如果用户点击它，它会将保存的歌曲添加到阵列中，当用户转到SavedVC故事板时，阵列中保存的所有项目都会显示为用户。单击按钮的功能如下所示。

@IBAction func save(_ sender: Any) {


    if(saveBtn.currentTitle == "Save"){

        song.saved = true
        let p1 = song
        savedSongs.append(p1)
        //UserDefaults save here
        saveBtn.setTitle("Unsave", for: .normal)
    }
    else if(saveBtn.currentTitle == "Unsave"){

        if(savedSongs.count != 0){
            //let items = (savedSongs.count) - 1

            let title = song.songTitle

            for save in 0...savedSongs.count-1{

                let removeSave = savedSongs[save]
                let checkTitle = removeSave.songTitle

                if(checkTitle == title){
                    song.saved = false
                    savedSongs.remove(at: save)
                    //UserDefaults save here
                    saveBtn.setTitle("Save", for: .normal)
                    return
                }
            }
        }
    }
}

很明显，用户可以选择保存，之后，他可以重新点击按钮取消保存歌曲。在代码中，对象

song.(attribute)

被发送并且是所选单元格的表示，其中包含Song类中的信息。因为我现在有我的代码，一切正常。问题是当我离开应用程序时，数组中的内容不会停留。我尝试过UserDefaults，但我不知道如何使用我拥有的数组。

每次在上面的保存IBAction中单击按钮时，我想将数组保存为用户默认值。

Answer 1

您需要对对象进行编码和解码，以便将它们保存到UserDefaults。

class Song: NSObject, NSCoding {
    let name: String
    let url: String

    init(name: String, url: String) {
        self.name = name
        self.url = url
    }

    required init(coder decoder: NSCoder) {
        self.name = decoder.decodeObject(forKey: "name") as? String ?? ""
        self.url = decoder.decodeInteger(forKey: "url") as? String ?? ""
    }

    func encode(with coder: NSCoder) {
        coder.encode(name, forKey: "name")
        coder.encode(age, forKey: "url")
    }
}

然后检索并保存：

class MyViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // SAVE TO DEFAULTS
        let song = Song(name: "Song", url: "http://song.com")
        var songs = [Song]()
        songs.append(song)
        let encodedData = NSKeyedArchiver.archivedData(withRootObject: songs)
        UserDefaults.standard.set(encodedData, forKey: "songs")

        // RETRIEVE FROM DEFAULTS
        if let data = UserDefaults.standard.data(forKey: "songs"),
            let mySongs = NSKeyedUnarchiver.unarchiveObject(with: data) as? [Song] {
            mySongs.forEach({print( $0.name, $0.url)})
        } else {
            print("ERROR")
        }
    }
}

如何使用UserDefaults保存包含已创建类的信息的数组

1 个答案: