How to get the current visible viewController from AppDelegate

Question

So, I'm using the method bellow from UIApplication extension to get the top view controller:

    class func topViewController(controller: UIViewController? = UIApplication.shared.keyWindow?.rootViewController) -> UIViewController? {
    if let navigationController = controller as? UINavigationController {
        return topViewController(controller: navigationController.visibleViewController)
    }
    if let tabController = controller as? UITabBarController {
        if let selected = tabController.selectedViewController {
            return topViewController(controller: selected)
        }
    }
    if let presented = controller?.presentedViewController {
        return topViewController(controller: presented)
    }
    return controller
}

But the problem is: It always returns UIViewController. But I need to check if it is MyViewController for example. How do I achieve that?

David Pasztor · Accepted Answer · 2017-09-06 14:47:41Z

5

Do conditional casting on the return value to safely check its type.

if let currentVC = UIApplication.topViewController() as? MyViewController {
   //the type of currentVC is MyViewController inside the if statement, use it as you want to
}

Your whole function implementation is flawed, if it actually worked, it would lead to infinite recursion. Once you find out the type of your current top view controller in your if statements, you are calling the same function again with the current root controller as its input value. Your function only ever exists, if it reaches either a call from a view controller, whose class is none of the ones specified in your optional bindings.

Moreover, your whole implementation doesn't do anything at the moment. You find out the type of your root view controller, but than you upcast it by returning a value of type UIViewController.

edited Sep 6, 2017 at 14:47

answered Sep 6, 2017 at 14:24

David Pasztor

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5 Comments

David Pasztor Over a year ago

Your question doesn't reflect your actual problem it seems. Have a look at my updated answer. Your implementation is completely flawed. What are you actually trying to do? Are you trying to return your rootViewController with its exact type instead of type UIViewController?

Zakaria Over a year ago

Thanks for the insights, i'll take that in consideration to update the topViewController method.

Capella Over a year ago

@DávidPásztor I cannot use topViewController in Swift 4.

David Pasztor Over a year ago

@SoftDev did you declare it as it is declared in the question itself?

steveSarsawa Over a year ago

Awesome sir it helps me lot.

MSU_Bulldog · Accepted Answer · 2017-09-06 14:27:03Z

2

You can do a conditional check with an if-let statement like this:

if let presented = controller?.presentedViewController as? MyViewController {
    // it is a MyViewController
}

You can also just directly check if the UIViewController is that type of class like this:

if controller?.presentedViewController is MyViewController {
    // it is a MyViewController
}

answered Sep 6, 2017 at 14:27

MSU_Bulldog

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Comments

Tom E · Accepted Answer · 2017-09-06 14:23:21Z

1

Try this:

if let presented = controller?.presentedViewController as? MyViewController {
    ...

answered Sep 6, 2017 at 14:23

Tom E

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Comments

Krunal · Accepted Answer · 2017-09-06 14:25:27Z

You can check it in following ways

class func topViewController(controller: UIViewController? = UIApplication.shared.keyWindow?.rootViewController) -> UIViewController? {
        if let navigationController = controller as? UINavigationController {
            return topViewController(controller: navigationController.visibleViewController)
        }
        else if let tabController = controller as? UITabBarController {
            if let selected = tabController.selectedViewController {
                return topViewController(controller: selected)
            }
        }
        else if let presented = controller?.presentedViewController {
            return topViewController(controller: presented)
        }
        return controller
}


        // Answer 
        if let topVC = AppDelegate.topViewController() as? MyViewController {
            // Here your topVC is MyViewController
        }


        // or 
        if let topVC = AppDelegate.topViewController() {

            if topVC is MyViewController {
                // Here your topVC is MyViewController
            }
        }

S.Moore · Accepted Answer · 2017-09-07 23:50:58Z

1

To use the UIViewController as MyViewController:

if let myViewController = UIApplication.topViewController() as? MyViewController { ... }

or if you just want to check that the UIViewController is of type MyViewController:

if UIApplication.topViewController() is MyViewController { ... }

edited Sep 7, 2017 at 23:50

answered Sep 6, 2017 at 14:26

S.Moore

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