UIViewController still in memory after calling dismiss - ios

Question

So I create a UICollectionViewController class along with a custom UICollectionViewCell. I am presenting a new UIViewController from the CollectionView and then dismissing it in the UIViewController in order to return to the CollectionView. Everything works except for the fact that after dismissing the UIViewController it still remains in memory which is not what I want. I would like to completely destroy the UIViewController once it is dismiss but cannot figure out how do it.
Am I doing anything wrong? Is it normal for the dismiss ViewController to remain in memory after it's dismissal?
// UICollectionViewController class
class MyCollection: UICollectionViewController, UICollectionViewDelegateFlowLayout {
let cellId = "cellId"
override func viewDidLoad() {
collectionView.register(CustomCell.self, forCellWithReuseIdentifier: cellId)
}
let viewControllers:[UIViewController] = [ViewController1()]
override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return viewControllers.count
}
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let activityCell = collectionView.dequeueReusableCell(withReuseIdentifier: cellId, for: indexPath) as! CustomCell
return activityCell
}
override func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let vc = viewControllers[indexPath.item]
present(vc, animated: true, completion: nil)
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: view.frame.width, height: 90)
}
}
// Custom UICollectionViewCell class
class CustomCell: UICollectionViewCell {
override init(frame: CGRect) {
super.init(frame: frame)
backgroundColor = .red
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
class ViewController1: UIViewController {
lazy var dismissButton: UIButton = {
let newButton = UIButton(type: .system)
newButton.setTitle("Dismiss", for: .normal)
newButton.backgroundColor = .red
newButton.addTarget(self, action: #selector(dismissView), for: .touchUpInside)
newButton.translatesAutoresizingMaskIntoConstraints = false
return newButton
}()
#objc func dismissView() {
dismiss(animated: true, completion: nil)
}
override func viewDidLoad() {
super.viewDidLoad()
view.addSubview(dismissButton)
NSLayoutConstraint.activate([
dissmissButton.centerXAnchor.constraint(equalTo: view.centerXAnchor)
dissmissButton.centerYAnchor.constraint(equalTo: view.centerYAnchor)
])
}
}

Answer 1

Reason why ViewController1 instance is not destroyed completely?
Even after the viewController is dismissed, you're still holding the reference to it inside MyCollection's viewControllers array.
Solution:
In case, you want a brand new instance of the controller everytime a cell is tapped, there is no need to store the controller in viewControllers array.
Simply update didSelectItemAt method to,
override func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let vc = ViewController1() //here......
present(vc, animated: true, completion: nil)
}

Answer 2

No you are not doing it wrong. There is no strong retain cycle within your code.
The only problem is, even after you dismiss your view controller, it still resides in here
let viewControllers:[UIViewController] = [ViewController1()]
If you want the instance to be destroyed completely you need to remove it from the array as well.

Answer 3

It's not a good choice to make a global variable of a viewController.Once you still hold it,you'll be unable to destroy it.Do it like this:
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
let vc:UIViewController?
switch indexPath.row {
case 0:
vc = ViewController1()
case 1:
vc = ViewController2()
default:
vc = ViewController0()
}
present(vc!, animated: true, completion: nil)
}
And if there are many viewControllers, maybe it will be better to create a Array of Class like this:
guard let nameSpace = Bundle.main.infoDictionary?["CFBundleName"] as? String else { return }
let clsName = String(format: "%#.%#", nameSpace, cList[indexPath.row])
let cls = (NSClassFromString(clsName) as? UIViewController.Type)!
let vc = cls.init()
present(vc, animated: true, completion: nil)
clist:let cList = ["FirstController","SecondController"]
PS:
Of course I would not use this route if I get 50 ViewControllers.I just think that we can just use the most convenient way to solve the problem.
Hope this will help you.