programmatic navigation back button not showing - ios

Question

here is my code at the appdelegate:
func showMainView()
{
self.window = UIWindow(frame: UIScreen.main.bounds)
let storyBoard : UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
let secondViewController = storyBoard.instantiateViewController(withIdentifier: "PRODUCT_TABBAR_VC_ID")
let nav = UINavigationController()
nav.pushViewController(secondViewController, animated: true)
self.window!.rootViewController = nav
self.window!.makeKeyAndVisible()
}
simulator output:
basicaly i want when user press back button then came back main page . i mean initial page .
i am trying with this one but it not working at least one answer for me Navigate Back to previous view controller
Note : #matt said it is imposible. so could you tell me please what should i do . i am new to iOS
Update:
when user select Man that time tabviewcontroller two page only showing list of product about Man. so if user want to see Woman then user back to main page to select Woman then he will see Woman tabviewcontroller two page.

Answer 1

The back button is for returning to an earlier view controller pushed onto a UINavigationController. In your code, there is no back button because there is nothing to come back to; secondViewController is the only view controller pushed onto the UINavigationController.

Answer 2

You should create your hierarchy like so:
----> UIViewController
----> UINavigationController ----> UIViewController ----> UITabBarController
----> UIViewController
EDIT: It will look like that:
This way it will be possible to pop UIViewControllers contained in UITabBarController.

Answer 3

Place following lines within didFinishLaunchingWithOptions in AppDelegate.swift
self.window = UIWindow(frame: UIScreen.main.bounds)
let nav = UINavigationController(rootViewController: FirstViewController())
self.window!.rootViewController = nav
self.window!.makeKeyAndVisible()
Create FirstViewController.swift with following:
class FirstViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let button1 = UIButton(frame: CGRect(x: 0, y: 0, width: 200, height: 200))
button1.setTitle("Man", for: .normal)
button1.tag = 1
self.view.addSubview(button1)
button1.addTarget(self, action: #selector(showAction(sender:)), for: .touchUpInside)
let button2 = UIButton(frame: CGRect(x: 0, y: 250, width: 200, height: 200))
button2.setTitle("Woman", for: .normal)
button2.tag = 2
self.view.addSubview(button2)
button2.addTarget(self, action: #selector(showAction(sender:)), for: .touchUpInside)
}
func showAction(sender: UIButton) {
let storyBoard : UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
let secondViewController = storyBoard.instantiateViewController(withIdentifier: "PRODUCT_TABBAR_VC_ID")
if (sender.tag == 1) {
// SHOW MAN
} else if (sender.tag == 2) {
// SHOW WOMAN
}
self.navigationController?.pushViewController(secondViewController, animated: true)
}
}