ios - 如何从@objc 函数在 UIViewController 之间传递数据数组

Question

我有一个子 UICollectionViewController，其中有一组图像。当我删除任何照片时，我想将该组更新后的图像发送回父级 UIViewController。同样在子 Controller 中，我有一个编程 View ，当我单击任何图像以展开它时调用它。当图像展开时，用户可以单击删除按钮从该阵列中删除照片。删除后我的数组已正确更新，但由于某些原因我无法将其发送回父级。我尝试使用委托(delegate)和协议(protocol)将其发回。这是我的子 Controller 代码:

protocol ListImagesDelegate {

    func receiveImagesUpdated(data: [String]?)
}

class ListImagesVC: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource {

// Properties
    var receivedImagesPath: [String]? = []
    var fullscreenImageView = UIImageView()
    var indexOfSelectedImage = 0
    var imagesAfterDelete: [String]? = []
    var delegate: ListImagesDefectDelegate?


override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)

        print("imagesAfterDelete: \(imagesAfterDelete ?? [])") // I'm getting the right number of images in this array.

        delegate?.receiveImagesUpdated(data: imagesAfterDelete)
    }


...
...

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

        print("Click on photo: \(indexPath.item + 1)")

        if let imagePath = receivedImagesPath?[indexPath.item] {

            guard let selectedImage = loadImageFromDiskWith(fileName: imagePath) else {return}

            setupFullscreenImageView(image: selectedImage)

            indexOfSelectedImage = indexPath.item
        }
    }

    private func setupFullscreenImageView(image: UIImage){

        fullscreenImageView = UIImageView(image: image)
        fullscreenImageView.frame = UIScreen.main.bounds
        fullscreenImageView.backgroundColor = .black
        fullscreenImageView.contentMode = .scaleAspectFit
        fullscreenImageView.isUserInteractionEnabled = true

        self.view.addSubview(fullscreenImageView)
        self.navigationController?.isNavigationBarHidden = true
        self.tabBarController?.tabBar.isHidden = true

        let deleteButton = UIButton(frame: CGRect(x: fullscreenImageView.bounds.maxX - 50, y: fullscreenImageView.bounds.maxY - 75, width: 30, height: 40))
        deleteButton.autoresizingMask = [.flexibleLeftMargin, .flexibleBottomMargin]
        deleteButton.backgroundColor = .black
        deleteButton.setImage(UIImage(named: "trashIcon"), for: .normal)
        deleteButton.addTarget(self, action: #selector(deleteButtonTapped), for: .touchUpInside)

        fullscreenImageView.addSubview(deleteButton)
    }

    @objc func deleteButtonTapped(button: UIButton!) {
        print("Delete button tapped")

        receivedImagesPath?.remove(at: indexOfSelectedImage)

        imagesAfterDelete = receivedImagesPath

        collectionView.reloadData()

        self.navigationController?.isNavigationBarHidden = false
        self.tabBarController?.tabBar.isHidden = false
        fullscreenImageView.removeFromSuperview()
    }

这是父 Controller :

var updatedImages: [String]? = []

...
...

extension NewAlbumVC: ListImagesDelegate {

    func receiveImagesUpdated(data: [String]?) {

        print("New array: \(data ?? [])") // This print is never called.

        updatedImages = data

    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

        if segue.identifier == "goToImages" {

            let listImagesVC = segue.destination as! ListImagesVC

            listImagesVC.delegate = self
        }
    }
}

我想指定我的子 Controller 设置了 Storyboard ID ("ListImagesID") 以及从父到子的 segue 标识符 ("goToImages")。会导致这有什么冲突吗？

感谢您阅读本文。

Answer 1

看来委托(delegate)在这里是nil

delegate?.receiveImagesUpdated(data: imagesAfterDelete)

为此

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

触发你必须有

self.performSegue(withIdentifier:"goToImages",sender:nil)

---

编辑:这个

let listImagesDefectVC = storyboard?.instantiateViewController(withIdentifier: "ListImagesDefectID") as!     ListImagesDefectVC
listImagesDefectVC.receivedImagesPath = imagesPath   
navigationController?.pushViewController(listImagesDefectVC, animated: true) 

不会触发 prepareForSegue ，所以添加

listImagesDefectV.delegate = self

最后

解决方案 1:

@objc func tapOnImageView() { 
     let listImagesDefectVC = storyboard?.instantiateViewController(withIdentifier: "ListImagesDefectID") as! ListImagesDefectVC
     listImagesDefectVC.receivedImagesPath = imagesPath 
     listImagesDefectVC.delegate = self
     navigationController?.pushViewController(listImagesDefectVC, animated: true)
 }

解决方案 2:

 @objc func tapOnImageView() {  
     self.performSegue(withIdentifier:"goToImages",sender:nil) 
 }

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

    if segue.identifier == "goToImages" {

        let listImagesVC = segue.destination as! ListImagesVC
        listImagesVC.receivedImagesPath = imagesPath 
        listImagesVC.delegate = self
    }
}