How can I use NSVisualEffectView to blend window with background - swift

Question

There seem to be a bunch of questions on this for old versions of Swift/Xcode, but for some reason it hasn't been working with the latest update. I created a NSVisualEffectView, blurryView, and added the subview to my main view:
class ViewController: NSViewController {
#IBOutlet weak var blurryView: NSVisualEffectView!
override func viewDidLoad() {
super.viewDidLoad()
//background styling
blurryView.wantsLayer = true
blurryView.blendingMode = NSVisualEffectBlendingMode.behindWindow
blurryView.material = NSVisualEffectMaterial.dark
blurryView.state = NSVisualEffectState.active
self.view.addSubview(blurryView, positioned: NSWindowOrderingMode.above, relativeTo: nil)
// Do any additional setup after loading the view.
}
...
}
But when I run it, there is no effect on the window. (when I set it to within window, and layer it on top of my other view, the blur works correctly, but I only want the window to blur.) I also tried doing the same thing in my App Delegate class, but I can't connect my window as an outlet, and therefore can't add the blurry view to the window. Here's what the code would look like:
class AppDelegate: NSObject, NSApplicationDelegate {
func applicationDidFinishLaunching(_ aNotification: Notification) {
// Insert code here to initialize your application
blurryView.wantsLayer = true
blurryView.blendingMode = NSVisualEffectBlendingMode.withinWindow
blurryView.material = NSVisualEffectMaterial.dark
blurryView.state = NSVisualEffectState.active
self.window.contentView?.addSubview(blurryView)
}
...
}
To get an idea if what I'm looking for: NSVisualEffectView Vibrancy

Answer 1

It works quite easy:
In Interface Builder drag a NSVisualEffectView directly as a subview of the main view of your scene.
In the Properties Inspector set Blending Mode to Behind Window
Add the rest of the views you need as subviews of the NSVisualEffectView
That's it, you're done
Here's an example:
Panel 1 View Controller is my blurred view, Background View is the first (non-blurred) view in my "real"view hierarchy.

Answer 2

Swift 5:
Simply add this to your viewWillAppear and it should work:
override func viewWillAppear() {
super.viewWillAppear()
//Adds transparency to the app
view.window?.isOpaque = false
view.window?.alphaValue = 0.98 //you can remove this line but it adds a nice effect to it
let blurView = NSVisualEffectView(frame: view.bounds)
blurView.blendingMode = .behindWindow
blurView.material = .fullScreenUI
blurView.state = .active
view.window?.contentView?.addSubview(blurView)
}