A CADisplayLink in a BindableObject

CADisplayLinkBinding.swift

//
//  CADisplayLinkBinding.swift
//  lingq-5
//
//  Created by Timothy Costa on 2019/07/11.
//  Copyright © 2019 timothycosta.com. All rights reserved.
//

import Combine
import SwiftUI

class CADisplayLinkBinding: NSObject, BindableObject {

	let didChange = PassthroughSubject<CADisplayLinkBinding, Never>()
	private(set) var progress: Double = 0.0

	private(set) var startTime: CFTimeInterval = 0.0
	private(set) var duration: CFTimeInterval = 0.0
	private(set) lazy var displayLink: CADisplayLink = {
		let link = CADisplayLink(target: self, selector: #selector(tick))
		link.add(to: .main, forMode: .common)
		link.isPaused = true
		return link
	}()

	func run(for duration: CFTimeInterval) {
		let now = CACurrentMediaTime()
		self.progress = 0.0
		self.startTime = now
		self.duration = duration
		self.displayLink.isPaused = false
	}

	@objc private func tick() {
		let elapsed = CACurrentMediaTime() - self.startTime
		self.progress = min(1.0, elapsed / self.duration)
		self.displayLink.isPaused = self.progress >= 1.0
		self.didChange.send(self)
	}

	deinit {
		self.displayLink.invalidate()
	}

}