How to dismiss a stack of UIViewControllers to a certain Root ViewController? - ios

Question

Some RootViewController presents a ParentViewController which than presents a ChildViewController.
How can I dissmiss the ChildViewController animated directly to the RootViewController whithout showing the ParentViewController again?
In Detail
Assume some presents the ParentViewController which lets the user enter some credentials to login to some user account.
Once the connection is established the ParentViewController presents the ChildViewController which shows connection / account details to the user
When the user closes the ChildViewController it should be dismissed animated (slide down, etc.). But instead of returning to the ParentViewController the user should get back directly to the RootViewController
Of course it would be possible, that the ParentViewController does not present the ChildViewController itself but (somehow) tells the RootViewController to this. This way it would be no problem to directly return from the ChildViewController to the RootViewController. However, this is NOT what I am looking for, since the RootViewController should not know about the ChildViewController or even care if the ParentViewController presents other VCs.
I am looking for a solution where the ParentViewController controls whether itself is shown after the VC it presented is dismissed or its parent (= the root VC).
Code:
typealias CompletionBlock = () -> Void
class RootViewController: UIViewController {
#IBAction func showParentVC(_ sender: Any) {
let parentVC = ParentViewController()
parentVC.completion = {
self.dismiss(animated: true, completion: nil)
}
present(parentVC, animated: true)
}
}
class ParentViewController: UIViewController {
var completion: CompletionBlock?
#IBAction func showChild(_ sender: Any) {
let childVC = ChildViewController()
childVC.completion = {
self.completion?()
}
present(childVC, animated: true)
}
}
class ChildViewController: UIViewController {
var completion: CompletionBlock?
#IBAction func close(_ sender: Any) {
completion?()
}
}
Using this code does NOT solve the described problem. If close is called on the ChildViewController the RootViewController calls self.dismiss(animated: true, completion: nil). This way the ChildViewController animates away and the ParentViewController becomes visible. Then the ParentViewController animates away and the RootViewControllerbecomes visible.
How to skip the ParentViewController and directly show the RootViewController after animating away the ChildViewController?

Answer 1

My recommendation is embed your RootViewController into a NavigationController (if you don't have it yet) and present both parent a child with
navigationController?.present(viewController, animated: true, completion: nil)
//instead of viewController.present(...)
And then youcan use this method from your childViewController
navigationController?.popToRootViewController(animated: true)

Answer 2

One approach would be to set the view's alpha to Zero when you present another VC onto the "stack" of presented VCs.
So, present the first modal VC from the "root" VC as normal. For each "child" that presents another VC, use:
present(vc, animated: true, completion: {
self.view.alpha = 0.0
})
Now, when you call-back to the "root" VC to dismiss all the VCs, you won't see the partial / flash of the intermediate VC / VCs.
Here is a complete example to test. No #IBOutlets or #IBActions ... just start with a black view controller and assign its Custom Class to MultiPresentDismissViewController:
import UIKit
class MultiPresentDismissViewController: UIViewController {
let theLabel: UILabel = {
let v = UILabel()
v.textAlignment = .center
v.font = UIFont.boldSystemFont(ofSize: 40)
v.backgroundColor = .yellow
v.text = "\"Root\" VC"
return v
}()
let showAnotherButton: UIButton = {
let v = UIButton()
v.backgroundColor = UIColor(white: 0.9, alpha: 1.0)
v.setTitle("Present a VC", for: .normal)
v.setTitleColor(.blue, for: .normal)
v.setTitleColor(.cyan, for: .highlighted)
return v
}()
let theStackView: UIStackView = {
let v = UIStackView()
v.axis = .vertical
v.alignment = .fill
v.distribution = .fill
v.spacing = 32
return v
}()
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .white
[theLabel, showAnotherButton].forEach {
theStackView.addArrangedSubview($0)
$0.layer.borderWidth = 1.0
}
theStackView.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(theStackView)
NSLayoutConstraint.activate([
theStackView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
theStackView.topAnchor.constraint(equalTo: view.topAnchor, constant: 100.0),
theStackView.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 0.8),
])
showAnotherButton.addTarget(self, action: #selector(presentAnotherVC), for: .touchUpInside)
}
#objc func presentAnotherVC() -> Void {
let vc = AnotherViewController()
vc.myID = 1
present(vc, animated: true, completion: nil)
}
}
class AnotherViewController: UIViewController {
let theLabel: UILabel = {
let v = UILabel()
v.textAlignment = .center
v.font = UIFont.boldSystemFont(ofSize: 100)
v.backgroundColor = .yellow
return v
}()
let showAnotherButton: UIButton = {
let v = UIButton()
v.backgroundColor = UIColor(white: 0.9, alpha: 1.0)
v.setTitle("Present Another VC", for: .normal)
v.setTitleColor(.blue, for: .normal)
v.setTitleColor(.cyan, for: .highlighted)
return v
}()
let defaultDismissButton: UIButton = {
let v = UIButton()
v.backgroundColor = UIColor(white: 0.9, alpha: 1.0)
v.setTitle("Default Dismiss All", for: .normal)
v.setTitleColor(.blue, for: .normal)
v.setTitleColor(.cyan, for: .highlighted)
return v
}()
let theStackView: UIStackView = {
let v = UIStackView()
v.axis = .vertical
v.alignment = .fill
v.distribution = .fill
v.spacing = 20
return v
}()
var myID: Int = 0
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .random()
[theLabel, showAnotherButton, defaultDismissButton].forEach {
theStackView.addArrangedSubview($0)
$0.layer.borderWidth = 1.0
}
theStackView.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(theStackView)
NSLayoutConstraint.activate([
theStackView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
theStackView.topAnchor.constraint(equalTo: view.topAnchor, constant: 100.0),
theStackView.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 0.8),
])
theLabel.text = "\(myID)"
showAnotherButton.addTarget(self, action: #selector(presentAnotherVC), for: .touchUpInside)
defaultDismissButton.addTarget(self, action: #selector(defaultDismissAll), for: .touchUpInside)
}
#objc func presentAnotherVC() -> Void {
let vc = AnotherViewController()
vc.myID = myID + 1
present(vc, animated: true, completion: {
self.view.alpha = 0.0
})
}
#objc func defaultDismissAll() -> Void {
// walk up the "presenting" hierarchy to find the "root" VC
var vc = self.presentingViewController
while vc?.presentingViewController != nil {
vc = vc?.presentingViewController
}
vc?.dismiss(animated: true, completion: nil)
}
}
extension CGFloat {
static func random() -> CGFloat {
return CGFloat(arc4random()) / CGFloat(UInt32.max)
}
}
extension UIColor {
static func random() -> UIColor {
return UIColor(red: .random(),
green: .random(),
blue: .random(),
alpha: 1.0)
}
}