How to flip a UIView with a 3D effect: transition(with:)

iOS has a built-in way to transition between views, and you can use this to produce 3D flips in just a few lines of code. Here's a basic example that flips between two views:

@objc func flip() {
    let transitionOptions: UIView.AnimationOptions = [.transitionFlipFromRight, .showHideTransitionViews]

    UIView.transition(with: firstView, duration: 1.0, options: transitionOptions, animations: {
        self.firstView.isHidden = true
    })

    UIView.transition(with: secondView, duration: 1.0, options: transitionOptions, animations: {
        self.secondView.isHidden = false
    })
}

Here's a basic test harness you can use to see that method in action:

var firstView: UIView!
var secondView: UIView!

override func viewDidLoad() {
    super.viewDidLoad()

    firstView = UIView(frame: CGRect(x: 32, y: 32, width: 128, height: 128))
    secondView = UIView(frame: CGRect(x: 32, y: 32, width: 128, height: 128))

    firstView.backgroundColor = UIColor.red
    secondView.backgroundColor = UIColor.blue

    secondView.isHidden = true

    view.addSubview(firstView)
    view.addSubview(secondView)

    perform(#selector(flip), with: nil, afterDelay: 2)
}

Try experimenting with the different values of UIView.AnimationOptions to see what other animations are available.