Updated 30 April 2021
In this Blog , we are going to learn about the deinitializer in Swift. Deinitializer is called in the Program to deallocate the memory space before a class instance deallocated from the Program. In Swift deinitializer are used to remove the Object which are not clean or removed by the ARC (Automatic Reference Counter).
So , In Order to Clean those reference we use deinitializer in Swift.
Deinitializer are called when the instance of a class is destroyed. For example the class car instance is created and its initialiser is called as soon as the instance is destroyed , init is called, which gives the advantage of house keeping after the destroy of the instanced the class.
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class Car { var name = "Maruti" init() { print("New Maruti is created") } deinit { print("Maruti is no more") } } |
For reference let take the example of the listener in the Firestore for listening for the changes in the data at run time.
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import FirebaseFirestore |
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class PeopleVC: UIViewController { //MARK:- @IBOutlet weak var tableView: UITableView! var peoples = [People]() var category: Category! var listener: ListenerRegistration! var db: Firestore! var locationManager: CLLocationManager! //let locationManager = CLLocationManager() //MARK:- viewLifecycleMethods override func viewDidLoad() { super.viewDidLoad() db = Firestore.firestore() setupTableView() // checkLocationServices() } override func viewWillAppear(_ animated: Bool) { fetchCollection() //setPeoples() } override func viewWillDisappear(_ animated: Bool) { listener.remove() } fileprivate func setupTableView() { tableView.dataSource = self tableView.delegate = self tableView.register(UINib(nibName: Identifiers.PeopleCell, bundle: nil), forCellReuseIdentifier: Identifiers.PeopleCell) tableView.rowHeight = UITableView.automaticDimension tableView.estimatedRowHeight = 200 } } //MARK:- UITableViewDataSource and UITableViewDelegate extension PeopleVC: UITableViewDataSource, UITableViewDelegate { func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int { return peoples.count } func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell { if let cell = tableView.dequeueReusableCell(withIdentifier: Identifiers.PeopleCell, for: indexPath) as? PeopleCell { cell.configureCell(people: peoples[indexPath.row]) return cell } return UITableViewCell() } func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) { let vc = PeopleDetailVC() let selectedPeople = peoples[indexPath.row] vc.people = selectedPeople vc.modalPresentationStyle = .overCurrentContext vc.modalTransitionStyle = .crossDissolve present(vc, animated: true, completion: nil) } // func tableView(_ tableView: UITableView, estimatedHeightForRowAt indexPath: IndexPath) -> CGFloat { // // return tableView.estimatedRowHeight // } // func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat { // // print(preferredContentSize.height) // print(tableView.contentSize.height) // print(tableView.contentSize) // // return 300 // } } //MARK:- getPeopleMethods extension PeopleVC { // By usinf the Reference Fetch the data func fetchCollection() { let collectionRef = db.collection("peoples").whereField("category", isEqualTo: category.id) listener = collectionRef.addSnapshotListener { (snap, error) in if let error = error { print(error.localizedDescription) return } self.peoples.removeAll() guard let documents = snap?.documents else { return } for document in documents { let data = document.data() let newPeople = People(data: data) self.peoples.append(newPeople) } self.tableView.reloadData() } } } |
As deist is used for removing listener in the above code.
we can use the deinitailzer for the cleaning up the Code. Please refer to my Other blog from here . For more information please refer to the Apple official from here.
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