Access accent color from Mac Catalyst app

AccentColorDemo.swift

//
//  ViewController.swift
//  UIKitAccentColor
//
//  Created by Jonny Kuang on 10/20/19.
//  Copyright © 2019 Jonny Kuang. All rights reserved.
//

import UIKit

class ViewController: UIViewController {

    #if targetEnvironment(macCatalyst)
    override func viewDidLoad() {
        super.viewDidLoad()
        
        view.backgroundColor = .kjy_controlAccentColor
        NotificationCenter.default.addObserver(self, selector: #selector(systemColorsDidChange), name: .init("NSSystemColorsDidChangeNotification"), object: nil)
    }
    
    @objc private func systemColorsDidChange() {
        print(#function)
        view.backgroundColor = .kjy_controlAccentColor
    }
    #endif
}


extension UIColor {
    #if targetEnvironment(macCatalyst)
    static var kjy_controlAccentColor: UIColor! { UIColor.value(forKey: "controlAccentColor") as? UIColor }
    #endif
}