ios - 取消 View 时更改值

我有一个NowPlayingVC，作为MainVC（一个集合视图）的子级，当第三个viewcontroller（SingleSoundVC）被解雇时，我想在NowPlayingVC中更改一个文本值。
我做任何事情都是通过代码，我不明白为什么解雇后我的标签仍然不可见。
如果我努力编码，它们工作得很好，但从不改变。

当第三个视图被删除但标签为空时，我可以正确地打印，即使我可以用调试视图层次结构看到它。
我尝试过这样的协议/委托：
协议

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

现在播放VC

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}

}
单声道VC

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")}

}

我还要补充一点，当我选择我现在添加的项目播放作为MainVC的代表时
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)
}

最佳答案

MainVC-集合视图
您应该为NowPlayingVC创建一个引用同一实例的属性：
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
应定义为：

    protocol SendDataToAudioPlayerContainer {
        func receiveData(data:Sound)
    }

现在播放VC
采用它来SendDataToAudioPlayerContainer协议：
添加

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

关于ios - 取消 View 时更改值，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/57540191/