How to pass array of data between UIViewControllers from #objc function - ios

Question

I have a Child UICollectionViewController where I have an array of images.
When I delete any photo I want to send back that array of updated images to Parent UIViewController.
Also in Child controller I have a programatically view which is called when I click on any image to expand it. When the image is expanded the user can click on a Delete button to delete photos from that array.
My array is updated correctly after delete but I can't manage to send it back to parent for some reasons.
I tried to send it back using Delegates and Protocols.
Here is my code for child controller:
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()
}
Here is the Parent 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
}
}
}
I want to specify that my child controller have set a Storyboard ID ("ListImagesID") and also a segue identifier from parent to child ("goToImages"). Can cause this any conflict ?
Thanks if you read this.

Answer 1

It appears that the delegate is nil here
delegate?.receiveImagesUpdated(data: imagesAfterDelete)
For this
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
to trigger you must have
self.performSegue(withIdentifier:"goToImages",sender:nil)
Edit: This
let listImagesDefectVC = storyboard?.instantiateViewController(withIdentifier: "ListImagesDefectID") as! ListImagesDefectVC
listImagesDefectVC.receivedImagesPath = imagesPath
navigationController?.pushViewController(listImagesDefectVC, animated: true)
doesn't trigger prepareForSegue , so add
listImagesDefectV.delegate = self
So finally
Solution 1 :
#objc func tapOnImageView() {
let listImagesDefectVC = storyboard?.instantiateViewController(withIdentifier: "ListImagesDefectID") as! ListImagesDefectVC
listImagesDefectVC.receivedImagesPath = imagesPath
listImagesDefectVC.delegate = self
navigationController?.pushViewController(listImagesDefectVC, animated: true)
}
Solution 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
}
}