Swift: Passing data between view controllers

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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
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*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)
}
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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) }
}
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So here is the complete code for:

ViewControllerA


import UIKit class 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) } } }
}
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*ViewControllerB
*


import UIKit class 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) }
}
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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 UIKit class 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 } }
}
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*ViewControllerB
*

import UIKit class ViewControllerB: UIViewController { var isSomethingEnabled = false override func viewDidLoad() { super.viewDidLoad() // Print value received through segue print("Value of 'isSomethingEnabled' from ViewControllerA: ", isSomethingEnabled) }
}
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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?)
}
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*Step 2. Declare Delegate variable instance in ViewControllerB
*

var delegate: ViewControllerBDelegate?
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Step 3. Send data for delegate inside viewDidLoad method of ViewControllerB

delegate?.addItemViewController(self, didFinishEnteringItem: "Data for ViewControllerA")
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*Step 4. Confirm ViewControllerBDelegate in ViewControllerA
*

class ViewControllerA: UIViewController, ViewControllerBDelegate {
// to do
}
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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) }
}
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Step 6. Implement delegate method for receiving data in ViewControllerA


func addItemViewController(_ controller: ViewControllerB?, didFinishEnteringItem item: String?) { print("Value from ViewControllerB's Delegate", item!)
}
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So here is the complete code for:

*ViewControllerA
*

import UIKit class 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) } } }
}
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*ViewControllerB
*

import UIKit
//Protocol decleare
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?)
} 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") }
}
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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 ?? "")
}
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So here is the complete code for:

*ViewControllerA
*

import UIKit class 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 ?? "") }
}
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ViewControllerB

import UIKit class 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) }
}
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_Passing Data through Block: From ViewControllerB to ViewControllerA
_
*Step 1. Declare block in ViewControllerB
*


var authorizationCompletionBlock:((Bool)->())? = {_ in}
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*Step 2. Set data in block in ViewControllerB
*

if authorizationCompletionBlock != nil
{ authorizationCompletionBlock!(true)
}
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Step 3. Receive block data in ViewControllerA

// Receiver Block
controller!.authorizationCompletionBlock = { isGranted in print("Data received from Block is: ", isGranted)
}
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So here is the complete code for:

ViewControllerA

import UIKit class 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) } } }
}
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ViewControllerB

import UIKit class 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) } }
}
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