关闭视图时更改值

Question

我有一个 NowPlayingVC，作为我的 MainVC（集合视图）的子级，我想在第三个视图控制器（SingleSoundVC）被解雇时更改 NowPlayingVC 内的 textValue。 我通过代码做所有事情，我不明白为什么我的标签在解雇后仍然不可见。 如果我尝试硬编码，它们工作得很好，但永远不会改变。

当第三个视图被关闭但标签为空时，我可以正确打印，即使我可以在调试视图层次结构中看到它。

我尝试过这样的协议/委托：

协议

protocol SendDataToAudioPlayerContainer {
func receiveData(data:Sound){
     self.audioNameLabel.text = data.name
   }
}

NowPlayingVC

NowPlayingVC: SendDataToAudioPlayerContainer
     var audioNameLabel:UILabel = {
        var lbl = UILabel()
        lbl.numberOfLines = 0
        lbl.textAlignment = .left
        lbl.sizeToFit()
        lbl.textColor = .black
        return lbl
    } 
    override func viewDidLoad() {
        super.viewDidLoad()
        setupViews()
        setupConstraints()
    }
  func setupViews() {
    self.view.backgroundColor = .blue
    self.view.addSubview(audioNameLabel)
}
 func setupConstraints(){ //setup of constraints with SnapKit}

}

SingleSoundVC

var delegate:SendDataToAudioPlayerContainer?
var singleSound: Sound?
@objc func dismissView(){

    if self.delegate != nil {
        print("data passed up")
        let data = self.singleSound
        delegate?.receiveData(data: data!)
        self.dismiss(animated: true, completion: nil)

    } else {self.dismiss(animated: true, completion: nil)
        print("data is not passed")}

}

我还必须补充一点，当我选择添加 NowPlaying 作为 MainVC 代表的项目时

MainVC - 集合视图

  func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

    let vc = MainVC()
    let childVC = NowPlayingVC()
    vc.delegate = childVC
    ApiService.sharedInstance.downloadAudioFile(with: vc.singleSound!.audioId)
    vc.modalPresentationStyle = .popover
    present(vc, animated: true, completion: nil)
}

Answer 1

MainVC - 集合视图

您应该为 NowPlayingVC 创建一个属性以引用同一个实例： var nowPlayingVC = NowPlayingVC()

  func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

    let vc = SingleSoundVC()
    vc.delegate = nowPlayingVC
    ApiService.sharedInstance.downloadAudioFile(with: vc.singleSound!.audioId)
    vc.modalPresentationStyle = .popover
    present(vc, animated: true, completion: nil)
}

协议

应该定义为：

    protocol SendDataToAudioPlayerContainer {
        func receiveData(data:Sound)
    }

NowPlayingVC

采用 SendDataToAudioPlayerContainer 协议： 添加

func receiveData(data:Sound){
         self.audioNameLabel.text = data.name
         **// update constraints here**
       }
    }