SampleKVO

gistfile1.txt

//
//  ViewController.swift
//  SampleObserve
//
//  Created by 永田大祐 on 2019/11/12.
//  Copyright © 2019 永田大祐. All rights reserved.
//

import UIKit

class ViewController: UIViewController {

    private var keyValueObservations = [NSKeyValueObservation]()

    override func viewDidLoad() {
        super.viewDidLoad()

        let kvo = observe(\.self.view?.backgroundColor, options: .new) { sss, change in
            guard let backgColor = change.newValue else { return }
            print(backgColor ?? UIColor.white)

        }
        keyValueObservations.append(kvo)
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(true)

        self.view?.backgroundColor = UIColor(red: 0.123, green: 0.456, blue: 0.789, alpha: 1)
        keyValueObservations.removeAll()
    }
}

func convertToRGB(_ color: UIColor) -> (red: CGFloat, green: CGFloat, blue: CGFloat, alpha: CGFloat) {

    let components = color.cgColor.components!
    return (red: components[0], green: components[1], blue: components[2], alpha: components[3])
}

UIExtendedSRGBColorSpace 0.123 0.456 0.789 1