how to present and dismiss at same time - ios

Question

This is my Code
#IBAction func backButton(_ sender: UIButton) {
self.dismiss(animated: true, completion: { () -> Void in
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let vc = storyboard.instantiateViewController(withIdentifier: "RequestItemPackageDetails") as! RequestItemPackageDetails
self.present(vc, animated: true, completion: nil)
})
}
this is not working only dissmising

Answer 1

I dont't understand your questions well. I think you want to present a new ViewController. You can use this:
UIView.animate{duration: 0.5, animations: {
(UIApplication.shared.delegate as! AppDelegate).window!.rootViewController = NextViewController()
}}

Answer 2

Problem is that you are dismissing self and then trying to present a new view controller on that exact same self - but at that moment self is already dismissed. You need to present that new view controller from the parent of the current view controller. I believe the best way is to setup a delegate. So the controller that you showed us and that you want to dismiss will have this:
protocol FirstDelegate: class {
func firstDismiss(_ first: First)
}
class First: UIViewController {
weak var delegate: FirstDelegate?
#IBAction func backButton(_ sender: UIButton) {
// this will tell the delegate to dismiss this contorller and present the other one
delegate?.firstDismiss(self)
}
// rest of the code omitted
}
Next, you will have to setup this in the parent that presents First view controller (here I assume that presentFirst method presents the First view controller):
class ParentViewController: UIViewController, FirstDelegate {
// rest of the code
func presentFirst() {
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let firstVC = storyboard.instantiateViewController(withIdentifier: "First") as! RequestItemPackageDetails
// set delegate to first:
firstVC.delegate = self
self.present(firstVC, animated: true, completion: nil)
}
func firstDismiss(_ first: First) {
first.dismiss(animated: true, completion: { () -> Void in
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let vc = storyboard.instantiateViewController(withIdentifier: "RequestItemPackageDetails") as! RequestItemPackageDetails
self.present(vc, animated: true, completion: nil)
})
}
}

Answer 3

Not quite sure with your Qns, but try this one out.
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let vc = storyboard.instantiateViewController(withIdentifier: "RequestItemPackageDetails") as! RequestItemPackageDetails
vc.previousVC = self
self.present(vc, animated: true)
RequestItemPackageDetails.swift
var previousVC : UIViewController!
override viewDidLoad() {
previousVC.dismiss(animated: false, completion: nil)
}

Answer 4

You can dismiss self and then present another view from rootViewController
self.dismiss(animated: true, completion: { () -> Void in
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let vc = storyboard.instantiateViewController(withIdentifier: "RequestItemPackageDetails") as! RequestItemPackageDetails
let appDelegate = UIApplication.shared.delegate as! AppDelegate
appDelegate.window!.rootViewController?.present(vc, animated: true, completion: nil)
})