A `UIScrollView` subclass that adapts its `intrinsicContentSize` to its `contentSize`

IntrinsicSizeAwareScrollView.swift

import Foundation
import UIKit

/// A `UIScrollView` subclass that adapts its `intrinsicContentSize` to its `contentSize`
final class IntrinsicSizeAwareScrollView: UIScrollView {
    
    private let keyPath = NSStringFromSelector(#selector(getter: contentSize))
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        addContentSizeObserver()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        addContentSizeObserver()
    }
    
    deinit {
        removeObserver(self, forKeyPath: keyPath)
    }
    
    override func observeValue(forKeyPath keyPath: String?,
                               of object: Any?,
                               change: [NSKeyValueChangeKey : Any]?,
                               context: UnsafeMutableRawPointer?) {
        
        if self.keyPath == keyPath {
            if let new = change?[.newKey] as? NSValue,
                let old = change?[.oldKey] as? NSValue,
                new != old {
                invalidateIntrinsicContentSize()
            }
        }
    }
    
    override var intrinsicContentSize: CGSize {
        return contentSize
    }
    
    private func addContentSizeObserver() {
        addObserver(self, forKeyPath: keyPath, options: [.new, .old], context: nil)
    }
}