How to push ViewController from outside of UIViewController or view?

I want to be able to navigate views from classes (singletons) in my app that have no connection to the views. The reason for this is that the data changes (for example as a result of networking calls) at some point after finishing displaying the views. For example the app (some class) may only know after one second if the user has opened the app before and should go to the main view, or see some onboarding view.

I have a UIViewController in a UINavigationController as the starting point of my app. The business logic is kept separate from the view part in Manager singletons that look like:

class ExampleManager: NSObject {
    
    static var shared: ExampleManager = ExampleManager()
    
    public override init() {
        super.init()
        
        SwiftSingletons.register(self)
    }
}

like this I can cross-communicate between them. Now let's say in one of the functions of this ExampleManager -1 second after its initialisation- the managers knows (implicitly by data) to navigate to view A or B. But how can I trigger a navigation to one of those views from within this manager?

I suspect this could either be done the following ways:

• using combine / notifications (observing the data inside the ViewController)
  • problem: this feels like a workaround for something very simple..
• using a static function inside the ViewController which can be called externally
  • problem: navigationController?.pushViewController(controller, animated: true) is not possible, since "Instance member 'navigationController' cannot be used on type 'ViewController'"
• or maybe there is some way like @ObservedObject in SwiftUI that triggers the view / ViewController to recalculate when data changes?

Sorry I don't have enough reputation to comment, but I would highly recommend you look into the coordinator pattern! It works in the same way that you're trying to use these singletons.

You give a VC a "coordinator" (just an object) and it handles navigating between views/VCs. The VCs themselves don't actually know who's connected to who, but the coordinator handles that.

https://www.hackingwithswift.com/articles/71/how-to-use-the-coordinator-pattern-in-ios-apps

To answer your question more directly, you'd give your object ExampleManager access to a navigationController or view controller, and it will handle pushing / popping, but it doesn't know exactly which view it's going to / from. (See the link I dropped above)