Send data only if view controller is being popped off stack by swipe or back button press but not by switching tabs

Question

I looked through SO and compiled these methods below but none of them works for me.

I have a TabBarController with 2 tabs. In the Second tab I have a NavigationController > TableViewController > DetailViewController.

In my DetailViewController I have a custom delegate to send some data to the TableViewController when the Back Button is pressed or the view is Swiped to Dismiss (right swipe). I only want the data sent when the Back Button or Swipe to Dismiss is fully finished and not get sent when the tab is switched or if swiping 3/4 of the way but the user decides NOT to complete the back swipe (basically they stay on the same DetailVC scene).

I tried all of these methods below and they either get triggered when the tab is switched to the first tab, when the DetailVC gets pushed on and popped off, or during the 1/2 way Swipe to Dismiss the DetailVC they still run meaning the data should not have been sent.

DetailViewController:

protocol DetailViewDelegate: class {
    func sendSomeData(value: Bool)
}

class DetailViewController: UIViewController{

weak var delegate: DetailViewDelegate?

//1. runs when Tab switches, the Back Button is pressed, and Swipe to Dismiss is triggered
override func viewWillDisappear(_ animated : Bool) {
        super.viewWillDisappear(animated)
        if (self.isMovingFromParentViewController) || (self.isBeingDismissed){
            //doesn't run at all
        }else{
            //runs whenever view is no longer on scene
            sendData()
        }
    }

//2. runs when Tab switches, Back Button is pressed, Swipe to Dismiss is triggered, and when the view is Pushed on AND Popped off
override func didMove(toParentViewController parent: UIViewController?) {
        if parent != nil {
            sendData()
        }else{
            //if parent == nil doesn't run at all
        }
    }

//3. if switching from the second tab it doesn't run but when switching back to the second tab it does run, also runs when view is being Pushed on and Not Popped on
func navigationController(_ navigationController: UINavigationController, willShow viewController: UIViewController, animated: Bool) {
         sendData()
    }

//4. if switching from the second tab it doesn't run but when switching back to the second tab it does run, also runs when view is being Pushed on and Not Popped on
func navigationController(_ navigationController: UINavigationController, didShow viewController: UIViewController, animated: Bool) {
         sendData()
    }

//MARK:- Custom Func
    fileprivate func sendData(){
        let value = true
        delegate?.sendSomeData(value: value)
    }
}

TableViewController:

class TableVC: UIViewController, DetailViewDelegate, UITableViewData..., UITableViewDele...{

var setValue = false

func sendSomeData(value: Bool){

     //setValue should only update to true if DetailVC's Back Button is pressed or Right Swipe to Dismiss is fully complete
     self.setValue = value
}

}

The TableView never has a problem receiving the data. The problem is when I switch tabs (data still gets sent) or a swipe to dismiss on the DetailVC isn't fully completed (data still gets sent).

What's the best way to send the data from the DetailVC but making sure the Back Button is pressed or Right Swipe to Dismiss is fully complete?

Answer 1

You need to use custom back button and a delegate to call the parent. this is your parent ViewController:

import UIKit

class ViewController: UIViewController, ViewControllerSecondDelegate {

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "Next" {
            let vc = segue.destination as? ViewControllerSecond
            vc?.delegate = self
        }
    }

    func secondDelegate() {
        print("delegate") //GetData()
    }

}

and this is the child view controller, which you want to back from it to your parent:

import UIKit

protocol ViewControllerSecondDelegate {
    func secondDelegate()
}

class ViewControllerSecond: UIViewController, UIGestureRecognizerDelegate {

    var isTouched = false
    var isPopTouch = true
    var delegate: ViewControllerSecondDelegate?

    override func viewDidLoad() {
        super.viewDidLoad()
        self.navigationController?.setNavigationBarHidden(false, animated:false)
        let myBackButton:UIButton = UIButton.init(type: .custom)
        myBackButton.addTarget(self, action: #selector(ViewControllerSecond.popToRoot(sender:)), for: .touchUpInside)
        myBackButton.setTitle("Back", for: .normal)
        myBackButton.setTitleColor(.blue, for: .normal)
        myBackButton.sizeToFit()
        let myCustomBackButtonItem:UIBarButtonItem = UIBarButtonItem(customView: myBackButton)
        self.navigationItem.leftBarButtonItem  = myCustomBackButtonItem
        self.navigationController?.interactivePopGestureRecognizer?.delegate = self
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        if isTouched {
            isPopTouch = true
        }
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        self.isPopTouch = false
    }

    override func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)
        if isPopTouch {
            delegate?.secondDelegate()
        }
    }

    func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
        if gestureRecognizer == self.navigationController?.interactivePopGestureRecognizer {
            self.isTouched = true
        }
        return true
    }

    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        self.isTouched = false
    }

    func popToRoot(sender:UIBarButtonItem){
        delegate?.secondDelegate()
        self.navigationController?.popToRootViewController(animated: true)
    }

}

the above code, handle back button and back gesture.