single function to dismiss all open view controllers

I have an app which is a single view application. I have a navigation controller linked up to all child controllers from the root view controller.

In each child controller, I have a logout button. I'm wondering if I can have a single function I can call which will dismiss all the controllers which have been open along along the way, no matter which controller was currently open when the user presses logout?

My basic start:

func tryLogout(){
     self.dismissViewControllerAnimated(true, completion: nil)
     let navigationController = UINavigationController(rootViewController: UIStoryboard(name: "Main", bundle: nil).instantiateViewControllerWithIdentifier("LoginViewController") )
     self.presentViewController(navigationController, animated: true, completion: nil)
}

I am looking for the most memory efficient way of carrying out this task. I will put my logout function in a separate utils file, but then I can't use self. And I still have the issue of knowing which controllers to dismiss dynamically.

Update Pop to root view controller has been suggested. So my attempt is something like:

func tryLogout(ViewController : UIViewController){
     print("do something")
     dispatch_async(dispatch_get_main_queue(), {
         ViewController.navigationController?.popToRootViewControllerAnimated(true)
         return
     })
 }

Would this be the best way to achieve what I'm after?

You can call :

self.view.window!.rootViewController?.dismiss(animated: false, completion: nil)

Should dismiss all view controllers above the root view controller.

Updated answer for Swift 4 and swift 5

UIApplication.shared.keyWindow?.rootViewController?.dismiss(animated: true, completion: nil)

and when you use navigationController

self.navigationController?.popToRootViewController(animated: true)

Works for Swift 4 and Swift 5

To dismiss any unwanted residue Modal ViewControllers, I used this and worked well without retaining any navigation stack references.

UIApplication.shared.keyWindow?.rootViewController?.dismiss(animated: false, completion: nil)

self.view.window! did crash for my case possibly because its a Modal screen and had lost the reference to the window.

Swift3

navigationController?.popToRootViewControllerAnimated(true)

Take a look at how unwind segues work. Its super simple, and lets you dismiss/pop to a certain viewcontroller in the heirarchy, even if it consists of a complex navigation (nested pushed and or presented view controllers), without much code.

Here's a very good answer (by smilebot) that shows how to use unwind segues to solve your problem https://stackoverflow.com/a/27463286/503527

To dismiss all modal Views.

Swift 5

view.window?.rootViewController?.dismiss(animated: true, completion: nil)

If you have a customed UITabbarController, then try dismiss top viewController in UITabbarController by:

class MainTabBarController: UITabBarController {

    func aFuncLikeLogout() {

        self.presentedViewController?.dismiss(animated: false, completion: nil)
        
        //......
    }

}

works for Swift 3.0 +

self.view.window!.rootViewController?.dismiss(animated: true, completion: nil)

I have figured out a generic function to dismiss all presented controllers using the completion block.

extension UIWindow {
    static func keyWindow() -> UIWindow? {
        UIApplication.shared.windows.filter({ $0.isKeyWindow }).first
    }
}

func getVisibleViewController(_ rootViewController: UIViewController?) -> UIViewController? {
    
    var rootVC = rootViewController
    if rootVC == nil {
        rootVC = UIWindow.keyWindow()?.rootViewController
    }
    
    var presented = rootVC?.presentedViewController
    if rootVC?.presentedViewController == nil {
        if let isTab = rootVC?.isKind(of: UITabBarController.self), let isNav = rootVC?.isKind(of: UINavigationController.self) {
            if !isTab && !isNav {
                return rootVC
            }
            presented = rootVC
        } else {
            return rootVC
        }
    }
    
    if let presented = presented {
        if presented.isKind(of: UINavigationController.self) {
            if let navigationController = presented as? UINavigationController {
                return navigationController.viewControllers.last!
            }
        }
        
        if presented.isKind(of: UITabBarController.self) {
            if let tabBarController = presented as? UITabBarController {
                if let navigationController = tabBarController.selectedViewController! as? UINavigationController {
                    return navigationController.viewControllers.last!
                } else {
                    return tabBarController.selectedViewController!
                }
            }
        }
        
        return getVisibleViewController(presented)
    }
    return nil
}

func dismissedAllAlert(completion: (() -> Void)? = nil) {

    if let alert = UIViewController.getVisibleViewController(nil) {

    // If you want to dismiss a specific kind of presented controller then
    // comment upper line and uncomment below one

    // if let alert = UIViewController.getVisibleViewController(nil) as? UIAlertController {

        alert.dismiss(animated: true) {
            self.dismissedAllAlert(completion: completion)
        }

    } else {
        completion?()
    }

}

Note: You call anywhere in code at any class

Use:-

dismissedAllAlert()    // For dismiss all presented controller

dismissedAllAlert {    // For dismiss all presented controller with completion block
    // your code
}

Swift Used this to jump directly on your ROOT Navigation controller.

self.navigationController?.popToRootViewController(animated: true)