Deinitializer in Swift

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.

class Car {
    var name = "Maruti"

    init() {
        print("New Maruti is created")
    }

    deinit {
        print("Maruti is no more")
    }
}

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.

import FirebaseFirestore

1	import FirebaseFirestore

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()
        }
    }
}

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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.

Conclusion

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.

deinitializer-in-swift swift

Vipin Kumar 30 April 2021

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Deinitializer in Swift

Deinitializer in Swift

Conclusion

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