🎇🎇🎆 One day I just needed to push a UINavigation from a UINavigation, well, easy.

@IBAction func push_nav(_ sender: Any) {
  let navVC = UINavigationController(rootViewController: ViewController())  
  navigationController?.pushViewController(navVC, animated: true)
}

• BrownVC (or NestedViewController) has an embed ViewController with UINavigationController as the embed VC.
• UINavigationController will present a VC with button “1”
• Button “1” will create another NestedViewController, blue one, and push BlueVC on to the Root UINavigation.
• We can repeat button “1” action multiple times.

  class NavViewController: UINavigationController {
    override func viewDidLoad() {
    super.viewDidLoad()  
    // we’ll work here in a bit  
  }

import UIKit  class NestedViewController: UIViewController {
  var rootVC: UIViewController  
  weak var rootNavigation: UINavigationController?  
  // 1  
  init(rootNavigation: UINavigationController) {  
    guard let vc = rootNavigation.viewControllers.first else { 
      fatalError(“root has not been initialized”)  
    }  
    self.rootVC = vc  
    self.rootNavigation = rootNavigation  
    super.init(nibName: nil, bundle: nil)  
  }  
  required init?(coder: NSCoder) {  
    fatalError(“init(coder:) has not been implemented”)  
  }  
  override func viewDidLoad() {  
    super.viewDidLoad()  
    // 2  
    let childNavigation = rootNavigation ?? UINavigationController(rootViewController: rootVC)  
    childNavigation.willMove(toParent: self)  
    addChild(childNavigation)  
    childNavigation.view.frame = view.frame  
    view.addSubview(childNavigation.view)  
    childNavigation.didMove(toParent: self)  
    childNavigation.navigationBar.isTranslucent = false  
    // 3  rootVC.navigationItem.leftBarButtonItem = 
    UIBarButtonItem(barButtonSystemItem: .close, target: nil, action: #selector(back))  
  }  
  @IBAction func back() {
    navigationController?.popViewController(animated: true)  
  }  
}

1. We create a new init method, taking in an UINavigationController and assign the UINavigationController to variable.
2. In viewDidLoad() we insert UINavigationController’s view to NestedViewController.
3. Add a back button (optional)

@IBAction func new_nav(_ sender: Any) {
  let cvc = UIStoryboard(name: “Main”, bundle: nil).instantiateViewController(identifier: “ViewController”)  
  let nestedVC = NestedViewController(rootNavigation: UINavigationController(rootViewController: cvc))  
  var nav = navigationController  
  while ((nav?.navigationController) != nil) {  
    nav = nav?.navigationController  
  }  
  DispatchQueue.main.async {  
    nestedVC.rootVC.navigationController?.navigationBar.barTintColor = UIColor.random()  
  }  
  nav?.pushViewController(nestedVC, animated: true)  
}

final class AlwaysPoppableDelegate: NSObject, UIGestureRecognizerDelegate {
  weak var navigationController: UINavigationController?  
  weak var originalDelegate: UIGestureRecognizerDelegate?  
  override func responds(to aSelector: Selector!) -> Bool {  
    if aSelector == #selector(gestureRecognizer(_:shouldReceive:)) { 
      return true 
    } else if let responds = originalDelegate?.responds(to: aSelector) {  
      return responds  
    } else {  
      return false  
    }  
  }  
  override func forwardingTarget(for aSelector: Selector!) -> Any? {  
    return originalDelegate  
  }  
  func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldReceive touch: UITouch) -> Bool {  
    return  true  
  }  
}  

protocol Nested {  
  var canNestedSwipeBack: Bool {get set}  
}

private let alwaysPoppableDelegate = AlwaysPoppableDelegate()

setNavigationBarHidden(true, animated: false)  
self.navigationBar.isOpaque = true  
alwaysPoppableDelegate.navigationController = self  
interactivePopGestureRecognizer?.delegate = alwaysPoppableDelegate

func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldReceive touch: UITouch) -> Bool {  
  if let nav = navigationController, nav.isNavigationBarHidden, nav.viewControllers.count > 1 {  
    // extra for nested nav viewcontrollers  
    if let nested = (nav.viewControllers.last as? Nested) {  
      return nested.canNestedSwipeBack  
    } else if let nestedVC = (nav.viewControllers.last as? NestedViewController) {  
      return (nestedVC.rootNavigation?.viewControllers.count ?? 0) <= 1  
    }  return true  
  } else if let result = originalDelegate?.gestureRecognizer?(gestureRecognizer, shouldReceive: touch) {  
    return result  
  } else {  
    return false  
  }  
}

@IBAction func same_nav(_ sender: Any) {  
  let cvc = UIStoryboard(name: “Main”, bundle: nil).instantiateViewController(identifier: “ViewController”)  
  navigationController?.pushViewController(cvc, animated: true)  
}