Deep Linking only working if app is running

Question

I have an app that uses deep linking to navigate to a page when a user shares specific content in the app with another user. This is working when the second user has the app already running, but if the app is not running it simply opens the app and remains on the main screen. I know I must be missing something really simple here, but I just can't figure it out and can't find any answers regarding this on google.

My code in AppDelegate.swift:

func application(_ application: UIApplication, open url: URL, sourceApplication: String?, annotation: Any) -> Bool {
        let urlPath : String = url.path as String!
        let urlHost : String = url.host as String!
        let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)

        if(urlHost != "example.com")
        {
            print("Call Not From Correct Host. Not Continuing...")
            return false
        }

        if(urlPath == "/articles"){

            let article: ArticleDetailsViewController = mainStoryboard.instantiateViewController(withIdentifier: "ArticleDetailsViewController") as! ArticleDetailsViewController
            self.window?.rootViewController = article
        } 
        self.window?.makeKeyAndVisible()
        return true
    }

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        // Override point for customization after application launch.

        return true
    }

Answer 1

This is correct behavior. You should handle it in appliction(_: didFinishLaunchingWithOptions:)

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    // Override point for customization after application launch.
    if let url = launchOptions[.url] as? URL, let annotation = launchOptions[.annotation] {
        return self.application(application, open: url, sourceApplication: launchOptions[.sourceApplication] as? String, annotation: annotation)
    }
    return true
}

Answer 2

For Swift4.2

if launchOptions != nil{
        let launch = launchOptions![UIApplicationLaunchOptionsKey.userActivityDictionary]! as! Dictionary <String,Any>

        if ((launch["UIApplicationLaunchOptionsUserActivityKey"]! as! NSUserActivity).webpageURL != nil){
            if defaults.bool(forKey: DEFAULTS_IS_FIRST_START){
                print((launch["UIApplicationLaunchOptionsUserActivityKey"]! as! NSUserActivity).webpageURL)
            }
        }
    }