gradient.swift

import Foundation
import UIKit
import PlaygroundSupport

extension String {
	func toColorIncludingAlpha() -> UIColor? {
		var cString: String = self
			.trimmingCharacters(in: .whitespacesAndNewlines)
			.replacingOccurrences(of: "#", with: "")

		guard cString.characters.count == 8 || cString.characters.count == 6 else { return nil }

		var rgbValue: UInt32 = 0
		Scanner(string: cString).scanHexInt32(&rgbValue)

		let blue = CGFloat(rgbValue & 0xff) / 255.0
		let green = CGFloat((rgbValue >> 8) & 0xff) / 255.0
		let red = CGFloat((rgbValue >> 16) & 0xff) / 255.0
		let alpha = cString.characters.count == 6 ? 1 : CGFloat((rgbValue >> 24) & 0xff) / 255.0
		return UIColor(red: red, green: green, blue: blue, alpha: alpha)
	}
}

private func colorBackground(view: UIView) {
	let hex = ["ff48adb6", "ffade13a"]
	let colors: [CGColor] = hex.flatMap({ $0.toColorIncludingAlpha() }).map({ $0.cgColor })

	let layer = CAGradientLayer()
	layer.frame = CGRect(x: 0.0, y: 0.0, width: view.frame.width, height: view.frame.height)
	layer.colors = colors

	layer.startPoint = CGPoint(x: 0.2, y: 1)
	layer.endPoint = CGPoint(x: 0.7, y: -0.6)

	// true corner-to-corner
//	layer.startPoint = CGPoint(x: 0, y: 1)
//	layer.endPoint = CGPoint(x: 1, y: 0)

	view.layer.addSublayer(layer)
}

let gradientController = UIViewController()

gradientController.view = UIView(frame: CGRect(x: 50, y: 50, width: 375, height: 667))
gradientController.view.backgroundColor = .blue

colorBackground(view: gradientController.view)

let navigation = UINavigationController(rootViewController: gradientController)

PlaygroundPage.current.liveView = navigation