[Rainbow Layer] Implementing "rainbow" layer with Swift Playground on iPad #swift #playground #iOS

HueGradientLayer.swift

//#-editable-code
// Additional Comments
//#-end-editable-code
// Contents.swift
// Rainbow
//
// Created by Apollo Zhu (https://github.com/ApolloZhu) on 2016/11/25.
// Copyright (c) 2015-2017 WWITDC. All rights reserved.
//
//#-editable-code
// Additional Frameworks and Libraries
//#-end-editable-code
//#-hidden-code
import UIKit
import PlaygroundSupport
//#-end-hidden-code
class HueGradientLayer: CAGradientLayer {
    //#-hidden-code
    override init() {
        super.init()
        setup()
    }
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        setup()
    }
    override init(layer: Any) {
        super.init(layer: layer)
        setup()
    }
    //#-end-hidden-code
    func setup() {
        //#-editable-code
        startPoint = CGPoint(x: 0.5, y: 0)
        endPoint = CGPoint(x:0.5, y: 1)
        let controls = [CGFloat](stride(from: 0, through: 1, by: 0.01))
        colors = controls.map {
            UIColor(hue: $0, saturation: 1, brightness: 1, alpha: 1).cgColor
        }
        locations = controls as [NSNumber]?
        //#-end-editable-code
    }
}
class HueGradientView: UIView {
    override open class var layerClass: AnyClass {
        return HueGradientLayer.self
    }
    //#-editable-code
    //#-end-editable-code
}
//#-hidden-code
var view: UIView = HueGradientView()
//#-end-hidden-code
view = HueGradientView()
//#-hidden-code
let vc = UIViewController()
PlaygroundPage.current.liveView = vc
vc.view = view
//#-end-hidden-code