My collection view is nil when implicit unwrapping? - swift

Question

I use a UITabBarController to manage the large middle button on the UITabBar. Here is a part of it.
class TabBarController: UITabBarController, UITabBarControllerDelegate, ContentChangedDelegate {
override func viewDidLoad() {
super.viewDidLoad()
setupMiddleButton()
}
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) {
AddViewController.delegate = self
performSegue(withIdentifier: "addEventSegue", sender: self)
}
}
and I conform another class LifeViewController(I used the class the specify the collecitonView and searchbar and other items in it) to tabBarController but the lifeCollectionView is always nil when implicitly unwrap, Could any one help me, Thank you so much!
class LifeViewController: TabBarController {
let realm = try! Realm()
var reminders : Results<Memorandum>!
let tabBarView = TabBarController()
#IBOutlet weak var searchBar: UISearchBar!
#IBOutlet var lifeCollectionView: UICollectionView!
override func viewDidLoad() {
super.viewDidLoad()
self.fetchData()
lifeCollectionView.delegate = self
lifeCollectionView.dataSource = self
// Do any additional setup after loading the view.
}
override func viewWillAppear(_ animated: Bool) {
self.fetchData()
}
override func reloadCollection() {
if let life = self.lifeCollectionView {
life.reloadData()
} else {
print("life found nil")
}
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
performSegue(withIdentifier: "editing", sender: self)
}
func fetchData() {
reminders = realm.objects(Memorandum.self)
}
}
//MARK: - CollectionView
extension LifeViewController {
override func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: lifeCollectionView.frame.width/2.1, height: lifeCollectionView.frame.width/2.1)
}
override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return reminders.count
}
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let reminder = reminders[indexPath.item]
let lifeCell = lifeCollectionView.dequeueReusableCell(withReuseIdentifier: "lifeCell", for: indexPath) as! ReminderCell
lifeCell.configureCell(date: reminder.dateReminder, importance: UIColor(hex: reminder.color)!, name: reminder.title, depict: reminder.depiction)
lifeCell.layer.cornerRadius = 12
return lifeCell
}
}
But when I change back to conform the LifeViewController to UIViewController, and other collection view protocols the IBOutlet, delegate and dataSource work again? Why is that?