Problem while passing data between multiple view controllers using push pop navigation - ios

Question

My work is
1 .Passing data from first view controller -> second view controller using pushViewController: Success
2 .Passing data from second view controller -> First View Controller using popViewController: Success //used delegate protocol for return data
3 .Passing data from third view controller -> First View Controller : Error
Code :
ViewController.swift
import UIKit
class ViewController: UIViewController,secondViewDelegate,thirddelegate {
#IBOutlet var Firstoutput: UILabel!
#IBOutlet var inputField: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
}
func popdata(value: String) { //second view controller delegate protocol defintions
Firstoutput.text = "\(value)"
}
func thirdView(datas:String) //third view controller delegate protocol definition
{
print(datas)
}
#IBAction func pushBtn(_ sender: Any) { //first view button action
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let vcFirst = storyboard.instantiateViewController(withIdentifier: "second") as! SecondViewController //secondview
vcFirst.Secondtext = inputField.text
vcFirst.delegate = self //second view delegate intiate
let vcThird = storyboard.instantiateViewController(withIdentifier: "third") as! ThirdViewController //third view
vcThird.thirddelegate = self //third view delegate intiate
navigationController?.pushViewController(vcFirst, animated: true)
}
}
SecondViewController.swift
import UIKit
//protocol for passing data when pop
protocol secondViewDelegate {
func popdata(value:String)
}
class SecondViewController: UIViewController {
#IBOutlet var secondOutputField: UILabel!
#IBOutlet var secondInputField: UITextField!
var Secondtext:String!
var delegate:secondViewDelegate!
override func viewDidLoad() {
super.viewDidLoad()
secondOutputField.text = Secondtext
}
//popping back to first view controller using data
#IBAction func popBtn(_ sender: Any) {
if delegate?.popdata != nil
{
delegate.popdata(value: secondInputField.text!)
}
navigationController?.popViewController(animated: true)
}
//pushing to third view controller
#IBAction func thirdPageBtn(_ sender: Any) {
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let vcThird = storyboard.instantiateViewController(withIdentifier: "third") as! ThirdViewController
navigationController?.pushViewController(vcThird, animated: true)
}
}
ThirdViewController.swift
import UIKit
protocol thirdviewDelegate //delegate to pass data from thirs view to first view
{
func thirdView(datas:String)
}
class ThirdViewController: UIViewController {
var thirddelegate:thirdviewDelegate!
#IBOutlet var thirdTextField: UITextField!
override func viewDidLoad() {
super.viewDidLoad
}
#IBAction func thirdViewInvoke(_ sender: Any) {
if thirddelegate?.thirdView != nil
{
thirddelegate.thirdView(datas: thirdTextField.text!)
}
}
}
OutPut Screenshot :
Only passing data from third to first view controller is not working help me to solve this issue...Thanking you

Answer 1

You can use NotificationCenter to receive data.
On press of your Get Data button in your ThirdViewController, post your notification.
let myDataToPass : [String: Any] = ["myData" : yourStringValue]
NotificationCenter.default.post(name: Notification.Name("getDataPressed"), object: myDataToPass)
In your FirstViewController, add observer in viewDidLoad that will listen for the notification:
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self, selector: #selector(receiveInitialDetails(notification:)), name: Notification.Name("getDataPressed"), object: nil)
}
//once the notification is received, this function will be called and you can get the data that you passed in thirdVC using notification.userInfo
#objc func receiveInitialDetails(notification : Notification) {
let data = notification.userInfo as! [String:Any]
let yourStringValue = data["myData"] as! String
// you have your data here. downcast it to your desired data type.
}

Answer 2

you can implement it by using notification center
below I give a small example how I pass imageDataDict in my project
let imageDataDict:[String: UIImage] = ["image": image]
// Post a notification
NSNotificationCenter.defaultCenter().postNotificationName(notificationName, object: nil, userInfo: imageDataDict)
// Register to receive notification in your class
NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(self.showSpinningWheel(_:)), name: notificationName, object: nil)
// handle notification
func showSpinningWheel(notification: NSNotification) {
if let image = notification.userInfo?["image"] as? UIImage {
// do something with your image
}
}

Answer 3

You can save the third view controller data to UserDefaults. Get data from User Defaults at first View controller :
`UserDefaults.standard.set(yourData, forKey: "yourDataKey")` // at third view controller
`UserDefaults.standart.string(forKey: "yourDataKey")` //first view controller
Hope it helps...

Answer 4

Reason your code not working:
As soon as you move to second view controller , your third view controller is deallocated from memory. Below line has no meaning in first view controller
let vcThird = storyboard.instantiateViewController(withIdentifier: "third") as! ThirdViewController //third view
vcThird.thirddelegate = self
You move to second view controller , third view controller is set to nil.
Either you can use NSNotificationCenter to move data from third to first.
If you want to go with protocols, than make below code change.
Code : ViewController.swift
Remove the code:
let vcThird = storyboard.instantiateViewController(withIdentifier: "third") as! ThirdViewController //third view
vcThird.thirddelegate = self
ThirdViewController.swift
protocol thirdviewDelegate //delegate to pass data from thirs view to first view
{
func thirdView(datas:String)
}
class ThirdViewController: UIViewController {
var thirddelegate:thirdviewDelegate?
#IBOutlet var thirdTextField: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
}
#IBAction func thirdViewInvoke(_ sender: Any) {
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let firstView = storyboard.instantiateViewController(withIdentifier: "first") as! ViewController //third view
self.thirddelegate = firstView
self.thirddelegate?.thirdView(datas: thirdTextField.text ?? "default value")
self.navigationController?.popToRootViewController(animated: true)
}
}