Present below current view and not above - swift

Question

I'm trying to present a view controller below another presented view controller (like WhatsApp when you open camera and press gallery).
I tried many things but none worked ..

Answer 1

Use child view controller and set view of that added child view controller at the top of hierarchy. It will be top most element, so actual background of this view will be obscured, but that's the way to go.
//code inside UIViewController class
func addViewControllerAtBottom() {
let newVC = NewVCType() //just instantiate it
addChildViewController(newVC)
view.insertSubview(newVC.view, at: 0) //at 0 means it's first rendered, all others will be on top of it
}

Answer 2

You can reproduce this behavior by doing the following :
First, create a NavigationController with a root ViewController :
let navController = UINavigationController(rootViewController: firstController)
Then, present this navigationController with animated: false and in the completion of the present method, push your second ViewController, still with animated: false (to avoid weird animations) :
present(navController, animated: false) {
navController.pushViewController(secondController, animated: false)
}
Here you go, you got a new navigation with 2 UIViewController, like WhatsApp.
Full code, wrapped into a button's action :
#IBAction func buttonTapped(_ sender: Any) {
let navController = UINavigationController(rootViewController: firstController)
present(navController, animated: false) {
navController.pushViewController(secondController, animated: false)
}
}