don't work reload data CollectionView - ios

Question

I have a collection in the ViewController1, if i click that it goes to ViewController2 where i can change a image; when i push back button on the navigation controller to go back in the ViewController1 i should see the image i changed in the ViewController2. My problem is that i need to reload the data of the CollectionView but i can't do it! I already tried to put CollectionView.reloaddata() in the **ViewWillAppear**, but nothing happened! How can i do this?
import UIKit
private let reuseIdentifier = "Cell2"
class CollectionViewControllerStatiVegetarian: UICollectionViewController {
let baza1 = Baza()
#IBOutlet var CollectionViewOut: UICollectionView!
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(true)
CollectionViewOut.reloadData()
}
override func viewDidLoad() {
super.viewDidLoad()
self.collectionView!.register(UICollectionViewCell.self, forCellWithReuseIdentifier: reuseIdentifier)
let backround = CAGradientLayer().turquoiseColor()
backround.frame = self.view.bounds
self.collectionView?.backgroundView = UIView()
self.collectionView?.backgroundView?.layer.insertSublayer(backround, at: 0)
}
override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
let size2 = baza1.superTuples(name: "2")
let x = Mirror(reflecting: size2).children.count //
return Int(x+1)
}
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell2", for: indexPath) as! CollectionViewCell_VegetarianStaty
if indexPath.row != 0 {
cell.shapka_stati_vegetarian.image = nil
let superTupl = baza1.superTuplesShapka(Nomer_tupl: (indexPath.row-1))
cell.label.text = superTupl.5
let tupl = baza1.superTuplesShapka(Nomer_tupl: (indexPath.row-1))
if (tupl.2 == 1) {
cell.shapka_stati_vegetarian.image = nil
cell.shapka_stati_vegetarian.image = UIImage(named: "fon_galochka.png")
} else {}
} else {
cell.shapka_stati_vegetarian.image = UIImage(named: "shapkastaty")
cell.label.text = ""
}
return cell
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
let screenWidth = UIScreen.main.fixedCoordinateSpace.bounds.width
let height = screenWidth*550/900+20
var size = CGSize(width: screenWidth, height: 73)
if indexPath.row==0 {
size = CGSize(width: screenWidth, height: height)
}
return size
}
override func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
if indexPath.row != 0 {
numb_cell = indexPath.row
let bazaSh = Baza()
let f = bazaSh.superTuplesShapka(Nomer_tupl: (indexPath.row-1) )
let vc = storyboard?.instantiateViewController(withIdentifier: "ViewStaty") as! ViewController
vc.obr = f.3
self.navigationController?.pushViewController(vc, animated: true)
}
}
}

Answer 1

Views are loaded only once in the lifetime of a view controller, so viewDidLoad is only run once.
One way to do this is to reload the data in viewWillAppear which is fired when the view appears, but this might run many times.
Another way is to have a delegate method of vc2 that is implemented by vc1. This delegate method is run when the data is changed in vc2 and since vc1 implements the delegate, it can then choose to reload the view.
Yet another way, and one that I prefer, is to use something like Core Data as a model. That way when vc2 changes the data, vc1 can be observing the state of objects it is interested in and react to changes in the model through the NSFetchedResultsControllerDelegate methods.
You could choose to use Realm as a persistence mechanism, and I'm sure there is a similar way to observe the model and react to changes.

Answer 2

inn order to reloadData in background thread, you need to use
DispatchQueue.main.async { self.collectionView.reloadData() }

Answer 3

implement your vc from
UICollectionViewDelegate , UICollectionViewDataSource
then in
viewDidLoad()
self.collectionView.delegate = self
self.collectionView.dataSource = self