access an array from another class - firebase

Question

what i want to do here is when i access the first album by pressing on the picture i should get pictures from firebase for that specific album but i have a problem with that and here is my code.
class albumsVC: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource{
#IBOutlet weak var collectionView: UICollectionView!
var posts = [Post]()
static var imageCache: NSCache<NSString, UIImage> = NSCache()
override func viewDidLoad() {
super.viewDidLoad()
collectionView.delegate = self
collectionView.dataSource = self
DataService.ds.REF_POSTS3.observe(.value, with: { (snapshot) in
if let snapshot = snapshot.children.allObjects as? [FIRDataSnapshot] {
for snap in snapshot {
print ("SNAP: \(snap)")
if let postDict = snap.value as? Dictionary<String, AnyObject>{
let key = snap.key
let post = Post(postKey: key , postData: postDict)
self.posts.append(post)
}
}
}
self.collectionView.reloadData()
})
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return posts.count
}
func numberOfSections(in collectionView: UICollectionView) -> Int {
return 1
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let post = posts[indexPath.row]
if let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath)as? collectionViewCellAlbums {
if let img = albumsVC.imageCache.object(forKey: post.mainImg as NSString) {
cell.configureCell(post: post, img: img)
return cell
}else {
cell.configureCell(post: post)
return cell
}
}
else {
return collectionViewCellAlbums()
}
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
self.performSegue(withIdentifier: "showAlbum", sender: self)
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?)
{
/**
if segue.identifier == "showAlbum"
{
let indexPaths = self.collectionView!.indexPathsForSelectedItems!
let indexPath = indexPaths[0] as IndexPath
let vc = segue.destination as! newViewController
let post = posts[indexPath.row]
if let img = CollectionVC.imageCache.object(forKey: post.imageUrl as NSString) {
vc.image = img
}
}
*/
}
}
I don't know how to access the array in the second class as shown in the picture for this function override func prepare(for segue
the class for the second array is exactly the same as the first one except the newViewController.swift
class newViewController: UIViewController {
#IBOutlet weak var imageView: UIImageView!
var image = UIImage()
override func viewDidLoad() {
super.viewDidLoad()
self.imageView.image = self.image
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
}

Answer 1

In class collectionVC you should have variable :
imageList
and in albumVC at:
prepare(for segue: UIStoryboardSegue, sender: Any?)
after
let vc = segue.destination as! newViewController
set :
vc.imageList = self.post.getAllImageOfPost()

Answer 2

In such cases using a singleton class solves the problem. In Singleton pattern you create instance just-in-time. This means when you set an array for example, this array will be allocated in memory until the program finishes running.
Refer to this link for Singleton implementation:
http://www.galloway.me.uk/tutorials/singleton-classes/