Apple a UIVibrancyEffect to an iOS navigation bar

VibrantNavigationBar.swift

override func viewWillAppear(animated: Bool) {

        // Make the bar actually transparent by setting an empty image as the background
        self.navigationController?.navigationBar.setBackgroundImage(UIImage(), forBarMetrics: .Default)
        self.navigationController?.navigationBar.shadowImage = UIImage()
        self.navigationController?.navigationBar.translucent = true
        var bounds = (self.navigationController?.navigationBar.bounds)!
        // make it cover the status bar by offseting y by -20
        bounds.offsetInPlace(dx: 0.0, dy: -20.0)
        bounds.size.height = bounds.height + 20.0
        
        // set the background to a UIVisualEffectView
        let visualEffectView = BlurredBackgroundView(frame: bounds)
        visualEffectView.autoresizingMask = [.FlexibleWidth, .FlexibleHeight]
        self.navigationController?.navigationBar.insertSubview(visualEffectView, atIndex: 0)
}

BlurredBackgroundView is a UIVisualEffectView like...
https://gist.github.com/cmmartin/c904e5a90ba89807c9bc