如何正确地将数据从Firebase传递到集合视图的NSObject类

如何正确地将数据发送到集合视图的自定义数据NSObject类?我的变量总是以零返回。

我在它自己的视图控制器中有一个启动屏幕。当我要加载的所有数据都从firebase加载完毕后,我通过 performSegue(withIdentifier:) SplashScreenViewController :

   func getDatabaseReference(){
    let d = DispatchGroup()
    d.enter()
    let encodedURL = (postIDRefDic["post1"]! + "/postURL")
    ref.child(encodedURL).observe(.value, with: { (snapshot) in
        let newUrl = snapshot.value as! String
        DemoSource.shared.url = newUrl
        d.leave()
    })
    d.notify(queue: .main){
        self.performSegue(withIdentifier: "showHome", sender: nil)
    }
}

在上面的代码中,您可以看到我正在切换到下一个视图控制器, HomeViewController DemoSource (上面也显示了)我正在使用它来分配我刚刚在该类中的变量中获得的新数据。这个 类是类型为的自定义数据类 NSObject :

import UIKit
import Firebase

struct DataObj {
    var image: UIImage?
    var play_Url: URL?
    var title = ""
    var content = ""
}

class DemoSource: NSObject {
static let shared = DemoSource()
var demoData = [DataObj]()
var url = ""

override init() {

    demoData += [
                  DataObj(image: #imageLiteral(resourceName: "ss-1") , play_Url: URL(string: url), title: "title ", content: "Description")
    ]
}

我将此类与HomeViewController一起用于集合视图:

import UIKit
import AVKit
import Firebase
import MMPlayerView


class HomeViewController: UIViewController {
    var offsetObservation: NSKeyValueObservation?
    lazy var mmPlayerLayer: MMPlayerLayer = {
    let l = MMPlayerLayer()
    l.cacheType = .memory(count: 5)
    l.coverFitType = .fitToPlayerView
    l.videoGravity = AVLayerVideoGravity.resizeAspect
    l.replace(cover: CoverA.instantiateFromNib())
    l.repeatWhenEnd = true
    return l
}()

@IBOutlet weak var playerCollect: UICollectionView!
override func viewDidLoad() {
    super.viewDidLoad()

    // remove previous download fails file
    MMPlayerDownloader.cleanTmpFile()
    self.navigationController?.mmPlayerTransition.push.pass(setting: { (_) in

    })
    offsetObservation = playerCollect.observe(\.contentOffset, options: [.new]) { [weak self] (_, value) in
        guard let self = self, self.presentedViewController == nil else {return}
        NSObject.cancelPreviousPerformRequests(withTarget: self)
        self.perform(#selector(self.startLoading), with: nil, afterDelay: 0.2)
    }
    playerCollect.contentInset = UIEdgeInsets(top: 0, left: 0, bottom: 200, right:0)
    DispatchQueue.main.asyncAfter(deadline: .now() + 1.0) { [weak self] in
        self?.updateByContentOffset()
        self?.startLoading()
    }

        mmPlayerLayer.getStatusBlock { [weak self] (status) in
            switch status {
            case .failed(let err):
                let alert = UIAlertController(title: "err", message: err.description, preferredStyle: .alert)
                alert.addAction(UIAlertAction(title: "OK", style: .default, handler: nil))
                self?.present(alert, animated: true, completion: nil)
            case .ready:
                print("Ready to Play")
            case .playing:
                print("Playing")
            case .pause:
                print("Pause")
            case .end:
                print("End")
            default: break
            }
        }
        mmPlayerLayer.getOrientationChange { (status) in
            print("Player OrientationChange \(status)")
        }
    }

deinit {

    offsetObservation?.invalidate()
    offsetObservation = nil
    print("ViewController deinit")
}

@IBAction func profileButtonTap(_ sender: Any) {
    let uid = (Auth.auth().currentUser?.uid)!
    let Splash = SpalshScreenViewController()
    Splash.GetProfilePicture(uid: uid)
    Splash.GetUsername(uid: uid)
    Splash.GetName(uid: uid)
    Splash.GetClipsNumber(uid: uid)
    Splash.GetFollowersNumber(uid: uid)
    Splash.GetFollowingsNumber(uid: uid)
    performSegue(withIdentifier: "showProfile", sender: nil)
}
}

extension HomeViewController: MMPlayerFromProtocol {
 func backReplaceSuperView(original: UIView?) -> UIView? {
    guard let path = self.findCurrentPath(),
        let cell = self.findCurrentCell(path: path) as? PlayerCell else {
        return original
    }
    return cell.imgView
}

// add layer to temp view and pass to another controller
var passPlayer: MMPlayerLayer {
    return self.mmPlayerLayer
}
func transitionWillStart() {
}
// show cell.image
func transitionCompleted() {
    self.updateByContentOffset()
    self.startLoading()
}
}
extension HomeViewController: UICollectionViewDelegateFlowLayout {
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
    let m = min(UIScreen.main.bounds.size.width, UIScreen.main.bounds.size.height)
    return CGSize(width: m, height: m*0.75)
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
   DispatchQueue.main.async { [unowned self] in
    if self.presentedViewController != nil || self.mmPlayerLayer.isShrink == true {
            //self.playerCollect.scrollToItem(at: indexPath, at: .centeredVertically, animated: true)
            //self.updateDetail(at: indexPath)
        } else {
            self.presentDetail(at: indexPath)
        }
    }
}

fileprivate func updateByContentOffset() {
    if mmPlayerLayer.isShrink {
        return
    }

    if let path = findCurrentPath(),
        self.presentedViewController == nil {
        self.updateCell(at: path)
        //Demo SubTitle
        if path.row == 0, self.mmPlayerLayer.subtitleSetting.subtitleType == nil {
           }
        }
    }
}

fileprivate func presentDetail(at indexPath: IndexPath) {
    self.updateCell(at: indexPath)
    mmPlayerLayer.resume()

    if let vc = UIStoryboard.init(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "DetailViewController") as? DetailViewController {
        vc.data = DemoSource.shared.demoData[indexPath.row]
        self.present(vc, animated: true, completion: nil)
    }
}

fileprivate func updateCell(at indexPath: IndexPath) {
    if let cell = playerCollect.cellForItem(at: indexPath) as? PlayerCell, let playURL = cell.data?.play_Url {
        // this thumb use when transition start and your video dosent start
        mmPlayerLayer.thumbImageView.image = cell.imgView.image
        // set video where to play
        mmPlayerLayer.playView = cell.imgView
        mmPlayerLayer.set(url: playURL)
    }
}

@objc fileprivate func startLoading() {
    self.updateByContentOffset()
    if self.presentedViewController != nil {
        return
    }
    // start loading video
    mmPlayerLayer.resume()
}

private func findCurrentPath() -> IndexPath? {
    let p = CGPoint(x: playerCollect.contentOffset.x + playerCollect.frame.width/2, y: playerCollect.frame.height/2)
    return playerCollect.indexPathForItem(at: p)
}

private func findCurrentCell(path: IndexPath) -> UICollectionViewCell? {
   return playerCollect?.cellForItem(at: path)
}
}

extension HomeViewController: UICollectionViewDataSource {
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return DemoSource.shared.demoData.count
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    if let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "PlayerCell", for: indexPath) as? PlayerCell {
        cell.data = DemoSource.shared.demoData[indexPath.row]
        return cell
    }
    return UICollectionViewCell()
}
}

我第一次实例化 Demosource 等级为:

extension HomeViewController: UICollectionViewDataSource {
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return DemoSource.shared.demoData.count
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    if let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "PlayerCell", for: indexPath) as? PlayerCell {
        cell.data = DemoSource.shared.demoData[indexPath.row]
        return cell
    }
    return UICollectionViewCell()
}
}

当我运行我的应用程序时,它显然崩溃了,数据类中的url是nil,即使我在splashscreenviewcontroller中设置了url?这个 演示源 类get在变量被填充之前就被实例化了,我用断点进行了一些调试。

所以我的问题是,在所有这些解释之后。。。为什么 类仍然为nil,为什么类在使用该类的视图仅在从Firebase获取数据后调用时才被执行?