How to reload the collectionview after dismiss a present modally view? - ios

Question

I have a tab bar with two tab bar item and I add a central addButton on it which can lead me to the adding items viewcontroller. Here is the setup of the middle button.
func setupMiddleButton() {
let tabBarHeight = tabBar.frame.size.height
let menuButton = UIButton(frame: CGRect(x: 0, y: 0, width: tabBarHeight*1.5, height: tabBarHeight*1.5))
var menuButtonFrame = menuButton.frame
menuButtonFrame.origin.y = view.bounds.height - menuButtonFrame.height/2 - tabBarHeight - 8
menuButtonFrame.origin.x = view.bounds.width/2 - menuButtonFrame.size.width/2
menuButton.frame = menuButtonFrame
menuButton.backgroundColor = UIColor.red
menuButton.layer.cornerRadius = menuButtonFrame.height/2
view.addSubview(menuButton)
let largeConfiguration = UIImage.SymbolConfiguration(scale: .large)
let addIcon = UIImage(systemName: "plus", withConfiguration: largeConfiguration)
menuButton.setImage((addIcon), for: .normal)
menuButton.addTarget(self, action: #selector(menuButtonAction(sender:)), for: .touchUpInside)
view.layoutIfNeeded()
}
#objc private func menuButtonAction(sender: UIButton) {
let addVC = AddViewController()
let navigationController = UINavigationController(rootViewController: addVC)
performSegue(withIdentifier: "addEventSegue", sender: sender)
}
and I did this in one of my tab bar view to reloadData, but I found the collectionView unable to reload after I end editing and dismiss the present modally
override func viewWillAppear(_ animated: Bool) {
lifeCollectionView.delegate = self
lifeCollectionView.dataSource = self
self.fetchData()
DispatchQueue.main.async {
self.lifeCollectionView.reloadData()
}
}
What should I do to reload the collection view after I dismiss that present modally? Thank you so much!

Answer 1

There are multiple ways to achieve that delegate , closure and modalPresentation Style
Way 1:
if you add navigationController.modalPresentationStyle = .fullScreen this will call viewWillAppear of the controller who presents controller and your reload method will get called
Way 2: Delegate & Protocol
Declare a protocol like the one below in Second Controller
protocol CallParent{
func reloadCollection()
}
Declare a property to hold the reference of view controller confirming to this protocol in Second Controller
weak var myParent : CallParent?
Now call reloadCollection before dismiss
if let parent = myParent {
parent.reloadCollection()
}
Confirm first controller with CallParent protocol
class FirstVC: UIViewController,CallParent{
Then while calling segue
#objc private func menuButtonAction(sender: UIButton) {
let addVC = AddViewController()
addVC.myParent = self
let navigationController = UINavigationController(rootViewController: addVC)
performSegue(withIdentifier: "addEventSegue", sender: sender)
}
Way 3 : In your presented controller call dismiss function like this
if let fvc = self.presentingViewController as? FirstController {
self.dismiss(animated: true) {
fvc.callReloadFunctionHere()
}
}
Way 4: Closure
class SecondViewController: UIViewController {
var onViewWillDisappear: (()->())?
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
onViewWillDisappear?()
}
...
}
In FirstController
#objc private func menuButtonAction(sender: UIButton) {
let addVC = AddViewController()
addVC.onViewWillDisappear = {
// reload collection view here
}
let navigationController = UINavigationController(rootViewController: addVC)
performSegue(withIdentifier: "addEventSegue", sender: sender)
}

Answer 2

Set your collection view datasource, delegate and reload only in viewDidLoad. You don't need to use viewWillAppear to reload your collectionView every time!
Use delegates to pass messages.
protocol ContentChangedDelegate: class {
func itemAdded()
}
Within AddViewController add the below variable
weak var delegate: ContentChangedDelegate? = nil
Set your the UIViewController subclass instance where the lifeCollectionView exists as delegate for AddViewController.
let addVC = AddViewController()
addVC.delegate = self
//push or present addVC
Conform your view controller to the ContentChangedDelegate protocol and within the itemAdded method you can reload your collection view.
Call delegate?.itemAdded() after adding your item in AddViewController. This would call the method in your listVC and it should update immediately.