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April 18, 2024 03:40 pm GMT

Swift: Passing data between view controllers

There are multiple options for passing data between view controllers.

Using Navigation Controller Push
Using Segue
Using Delegate
Using Notification Observer
Using Block

*Step 1. Declare variable in ViewControllerB
*

var isSomethingEnabled = false

*Step 2. Print Variable in ViewControllerB' ViewDidLoad method
*

override func viewDidLoad() {    super.viewDidLoad()    // Print value received through segue, navigation push    print("Value of 'isSomethingEnabled' from ViewControllerA: ", isSomethingEnabled)}

Step 3. In ViewControllerA Pass Data while pushing through Navigation Controller

if let viewControllerB = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "ViewControllerB") as? ViewControllerB {    viewControllerB.isSomethingEnabled = true    if let navigator = navigationController {        navigator.pushViewController(viewControllerB, animated: true)    }}

So here is the complete code for:

ViewControllerA

import UIKitclass ViewControllerA: UIViewController  {    override func viewDidLoad() {        super.viewDidLoad()    }    // MARK: Passing data through navigation PushViewController    @IBAction func goToViewControllerB(_ sender: Any) {        if let viewControllerB = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "ViewControllerB") as? ViewControllerB {            viewControllerB.isSomethingEnabled = true            if let navigator = navigationController {                navigator.pushViewController(viewControllerB, animated: true)            }        }    }}

*ViewControllerB
*

import UIKitclass ViewControllerB: UIViewController {    // MARK:  - Variable for Passing Data through Navigation push    var isSomethingEnabled = false    override func viewDidLoad() {        super.viewDidLoad()        // Print value received through navigation push        print("Value of 'isSomethingEnabled' from ViewControllerA: ", isSomethingEnabled)    }}

Passing Data through Segue: From ViewControllerA to ViewControllerB

Step 1. Create Segue from ViewControllerA to ViewControllerB and give Identifier = showDetailSegue in Storyboard as shown below

**
Step 2. In ViewControllerB Declare a viable named isSomethingEnabled and print its value.**
**
Step 3. In ViewControllerA pass isSomethingEnabled's value while passing Segue**

So here is the complete code for:

*ViewControllerA
*

import UIKitclass ViewControllerA: UIViewController  {    override func viewDidLoad() {        super.viewDidLoad()    }    // MARK:  - - Passing Data through Segue  - -    @IBAction func goToViewControllerBUsingSegue(_ sender: Any) {        performSegue(withIdentifier: "showDetailSegue", sender: nil)    }    // Segue Delegate Method    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {        if (segue.identifier == "showDetailSegue") {            let controller = segue.destination as? ViewControllerB            controller?.isSomethingEnabled = true//passing data        }    }}

*ViewControllerB
*

import UIKitclass ViewControllerB: UIViewController {    var isSomethingEnabled = false    override func viewDidLoad() {        super.viewDidLoad()        // Print value received through segue        print("Value of 'isSomethingEnabled' from ViewControllerA: ", isSomethingEnabled)    }}

Passing Data through Delegate: From ViewControllerB to ViewControllerA

Step 1. Declare Protocol ViewControllerBDelegate in the ViewControllerB file, but outside the class

protocol ViewControllerBDelegate: NSObjectProtocol {    // Classes that adopt this protocol MUST define    // this method -- and hopefully do something in    // that definition.    func addItemViewController(_ controller: ViewControllerB?, didFinishEnteringItem item: String?)}

*Step 2. Declare Delegate variable instance in ViewControllerB
*

var delegate: ViewControllerBDelegate?

Step 3. Send data for delegate inside viewDidLoad method of ViewControllerB

delegate?.addItemViewController(self, didFinishEnteringItem: "Data for ViewControllerA")

*Step 4. Confirm ViewControllerBDelegate in ViewControllerA
*

class ViewControllerA: UIViewController, ViewControllerBDelegate  {// to do}

Step 5. Confirm that you will implement a delegate in ViewControllerA

if let viewControllerB = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "ViewControllerB") as? ViewControllerB {    viewControllerB.delegate = self//confirming delegate    if let navigator = navigationController {        navigator.pushViewController(viewControllerB, animated: true)    }}

Step 6. Implement delegate method for receiving data in ViewControllerA

func addItemViewController(_ controller: ViewControllerB?, didFinishEnteringItem item: String?) {    print("Value from ViewControllerB's Delegate", item!)}

So here is the complete code for:

*ViewControllerA
*

import UIKitclass ViewControllerA: UIViewController, ViewControllerBDelegate  {    override func viewDidLoad() {        super.viewDidLoad()    }    // Delegate method    func addItemViewController(_ controller: ViewControllerB?, didFinishEnteringItem item: String?) {        print("Value from ViewControllerB's Delegate", item!)    }    @IBAction func goToViewControllerForDelegate(_ sender: Any) {        if let viewControllerB = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "ViewControllerB") as? ViewControllerB {            viewControllerB.delegate = self            if let navigator = navigationController {                navigator.pushViewController(viewControllerB, animated: true)            }        }    }}

*ViewControllerB
*

import UIKit//Protocol decleareprotocol ViewControllerBDelegate: NSObjectProtocol {    // Classes that adopt this protocol MUST define    // this method -- and hopefully do something in    // that definition.    func addItemViewController(_ controller: ViewControllerB?, didFinishEnteringItem item: String?)}class ViewControllerB: UIViewController {    var delegate: ViewControllerBDelegate?    override func viewDidLoad() {        super.viewDidLoad()        // MARK:  - - - -  Set Data for Passing Data through Delegate  - - - - - -        delegate?.addItemViewController(self, didFinishEnteringItem: "Data for ViewControllerA")    }}

Passing Data through Notification Observer: From ViewControllerB to ViewControllerA

Step 1. Set and post data in the notification observer in ViewControllerB

let objToBeSent = "Test Message from Notification"
NotificationCenter.default.post(name: Notification.Name("NotificationIdentifier"), object: objToBeSent)
*Step 2. Add Notification Observer in ViewControllerA
*
NotificationCenter.default.addObserver(self, selector: #selector(self.methodOfReceivedNotification(notification:)), name: Notification.Name("NotificationIdentifier"), object: nil)
*Step 3. Receive Notification data value in ViewControllerA
*

@objc func methodOfReceivedNotification(notification: Notification) {    print("Value of notification: ", notification.object ?? "")}

So here is the complete code for:

*ViewControllerA
*

import UIKitclass ViewControllerA: UIViewController{    override func viewDidLoad() {        super.viewDidLoad()        // Add observer in controller(s) where you want to receive data        NotificationCenter.default.addObserver(self, selector: #selector(self.methodOfReceivedNotification(notification:)), name: Notification.Name("NotificationIdentifier"), object: nil)    }    // MARK: Method for receiving Data through Post Notification    @objc func methodOfReceivedNotification(notification: Notification) {        print("Value of notification: ", notification.object ?? "")    }}

ViewControllerB

import UIKitclass ViewControllerB: UIViewController {    override func viewDidLoad() {        super.viewDidLoad()        // MARK:Set data for Passing Data through Post Notification        let objToBeSent = "Test Message from Notification"        NotificationCenter.default.post(name: Notification.Name("NotificationIdentifier"), object: objToBeSent)    }}

_Passing Data through Block: From ViewControllerB to ViewControllerA
_
*Step 1. Declare block in ViewControllerB
*

var authorizationCompletionBlock:((Bool)->())? = {_ in}

*Step 2. Set data in block in ViewControllerB
*

if authorizationCompletionBlock != nil{    authorizationCompletionBlock!(true)}

Step 3. Receive block data in ViewControllerA

// Receiver Blockcontroller!.authorizationCompletionBlock = { isGranted in    print("Data received from Block is: ", isGranted)}

So here is the complete code for:

ViewControllerA

import UIKitclass ViewControllerA: UIViewController  {    override func viewDidLoad() {        super.viewDidLoad()    }    // MARK:Method for receiving Data through Block    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {        if (segue.identifier == "showDetailSegue") {            let controller = segue.destination as? ViewControllerB            controller?.isSomethingEnabled = true            // Receiver Block            controller!.authorizationCompletionBlock = { isGranted in                print("Data received from Block is: ", isGranted)            }        }    }}

ViewControllerB

import UIKitclass ViewControllerB: UIViewController {    // MARK: Variable for Passing Data through Block    var authorizationCompletionBlock:((Bool)->())? = {_ in}    override func viewDidLoad() {        super.viewDidLoad()        // MARK: Set data for Passing Data through Block        if authorizationCompletionBlock != nil        {            authorizationCompletionBlock!(true)        }    }}

Original Link: https://dev.to/anurag31oct/swift-passing-data-between-view-controllers-46l5

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