How to fade a UIVisualEffectView and/or UIBlurEffect in and out?

I think this is new in iOS9, but you can now set the effect of a UIVisualEffectView inside an animation block:

let overlay = UIVisualEffectView()
// Put it somewhere, give it a frame...
UIView.animate(withDuration: 0.5) {
    overlay.effect = UIBlurEffect(style: .light)
}

Set it to nil to remove.

VERY IMPORTANT – When testing this on the simulator, make sure to set your simulator’s Graphics Quality Override to High Quality in order for this to work.