Split UICollectionView & UICollectionViewDataSource shows black screen - ios

Question

I'm starting a new project with a collection view that will be downloading a lot of data from a REST api. I've split the collection view and datasource into two files, but when I run the application, all I get is a black screen. I've seen a few questions and tried changing the background, adding the collection view as a subview, and nothing seems to be working. I don't run into any errors and the debug view hierarchy and the views are listed (back to front) as UIWindoW -> MainSearchVC -> UICollectionView.
I originally thought no cells were being filled in, but they should be since I set a UIImage in the cells. I'm not sure where else to look for this. My code is below - if anyone has experience with splitting the collection view from it's datasource or why things aren't working, please help:)
class AppDelegate: UIResponder, UIApplicationDelegate {
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
window = UIWindow(frame: UIScreen.main.bounds)
window?.makeKeyAndVisible()
window?.rootViewController = MainSearchVC()
return true
}
}
class MainSearchVC: UICollectionViewController {
init(){
super.init(collectionViewLayout: UICollectionViewFlowLayout())
self.collectionView = UICollectionView(frame: self.view.frame, collectionViewLayout: UICollectionViewFlowLayout())
self.collectionView?.dataSource = MainSearchDataSource()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
collectionView?.register(ImageCell.self, forCellWithReuseIdentifier: "imagecell")
}
override func viewDidLoad() {
super.viewDidLoad()
self.collectionView?.backgroundColor = UIColor.clear
self.collectionView?.tintColor = UIColor.blue
NSLog("Visible Cells: " + String(describing: self.collectionView?.visibleCells.count))
self.view.addSubview(self.collectionView!)
}
}
class MainSearchDataSource: NSObject, UICollectionViewDataSource {
func numberOfSections(in collectionView: UICollectionView) -> Int {
return 1;
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 10
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "imagecell", for: indexPath)
cell.backgroundColor = UIColor.red
return cell
}
}
class ImageCell: UICollectionViewCell {
override init(frame: CGRect) {
super.init(frame: frame)
setupViews()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
let imageView: UIImageView = {
let iv = UIImageView()
iv.image = UIImage(contentsOfFile: "SR71")
iv.contentMode = .scaleAspectFill
return iv
}()
func setupViews(){
addSubview(imageView)
imageView.frame = CGRect(x: 0, y: 0, width: frame.width, height: frame.width)
}
}

Answer 1

Problem with your MainSearchVC collection view dataSource delegate
First you should understand the Zeroing Weak Reference
dataSource delegate is maintaining a weak reference to your Object of MainSearchDataSource. And your statement is
self.collectionView?.dataSource = MainSearchDataSource()
Just allocated and assigned. It will not retain the datasource object.
You have to create a class variable and assign the MainSearchDataSource object. It will hold the object reference until MainSearchVC deallocate from memory.
class MainSearchVC: UICollectionViewController {
var searchDataSource: MainSearchDataSource?
init(){
super.init(collectionViewLayout: UICollectionViewFlowLayout())
self.collectionView = UICollectionView(frame: self.view.frame, collectionViewLayout: UICollectionViewFlowLayout())
searchDataSource = MainSearchDataSource()
self.collectionView?.dataSource = searchDataSource
}
// Remaining code of your `MainSearchVC`
}