Helper classes to make basic view controller transitions easier

// Return the views which shoud be animated in the transition
func viewsToAnimate() -> [UIView]

// Return a copy of the view which is passed in. The passed in view is one of the views to animate
func copyForView(subView: UIView) -> UIView

/* Optionally return the frames for the views which should be
   animated. This is needed sometimes because for example
   with custom container view contrllers the transitioning code
   can't figure out where on screen the view is actually visible
   when loaded. */
optional func frameForView(subView: UIView) -> CGRect

import UIKit

class ViewController: UIViewController, TransitionInfoProtocol {

    @IBOutlet weak var imageView: UIImageView!
    @IBOutlet weak var label: UILabel!
    
    func viewsToAnimate() -> [UIView] {
        return [imageView, label]
    }
    
    func copyForView(subView: UIView) -> UIView {
        if subView == imageView {
            let imageViewCopy = UIImageView(image: imageView.image)
            imageViewCopy.contentMode = imageView.contentMode
            imageViewCopy.clipsToBounds = true
            return imageViewCopy
        } else if subView == label {
            let labelCopy = UILabel()
            labelCopy.text = label.text
            labelCopy.font = label.font
            labelCopy.backgroundColor = view.backgroundColor
            return labelCopy
        }
        return UIView()
    }
}

import UIKit

class DetailViewController: UIViewController, TransitionInfoProtocol {

    @IBOutlet weak var imageView: UIImageView!
    @IBOutlet weak var label: UILabel!
    
    func viewsToAnimate() -> [UIView] {
        return [imageView, label]
    }
    
    func copyForView(subView: UIView) -> UIView {
        if subView == imageView {
            let imageViewCopy = UIImageView(image: imageView.image)
            imageViewCopy.contentMode = imageView.contentMode
            imageViewCopy.clipsToBounds = true
            return imageViewCopy
        } else if subView == label {
            let labelCopy = UILabel()
            labelCopy.text = label.text
            labelCopy.font = label.font
            labelCopy.backgroundColor = label.backgroundColor
            return labelCopy
        }
        return UIView()
    }
}