Extension for instance Storyboard one Controller

ExtensionUIViewController.swift

// Variant 1
extension UIViewController {
    static func instance<T: UIViewController>() -> T? {
        let name = String(describing: self)
        let storyboard = UIStoryboard(name: name, bundle: nil)
        let controller = storyboard.instantiateViewController(withIdentifier: name)
        return controller as? T
    }
}

// Required init type `vc` else compilator not understand return type 
guard let vc: VC = VC.instance() else { return }

// Variant 2
extension UIViewController {
    private class func instancePrivate<T: UIViewController>() -> T? {
        let name = String(describing: self)
        let storyboard = UIStoryboard(name: name, bundle: nil)
        return storyboard.instantiateInitialViewController(withIdentifier: name) as? T
    }
    class func instance() -> Self? {
        return instancePrivate()
    }
}

// Vairant 3
// Source https://gist.github.com/hamsternik/bf2ab86cd0f3fa3e1ccad69cb09e53bd

extension UIViewController {
    private class func storyboardInstancePrivate<T: UIViewController>() -> T? {
        let storyboard = UIStoryboard(name: String(describing: self), bundle: nil)
        return storyboard.instantiateInitialViewController() as? T
    }
    class func storyboardInstance() -> Self? {
        return storyboardInstancePrivate()
    }
}