Inside gradient color UIBezierPath - swift

Question

I need to fill my bezier path with a gradient color. I can fill the background on the graph but not the content of the bezier. Any idea why?
//: Playground - noun: a place where people can play
import Foundation
import UIKit
import CoreGraphics
import QuartzCore
class DemoView: UIView {
override func draw(_ rect: CGRect) {
let origin = CGPoint(x: frame.size.width / 2, y: frame.size.height / 2)
let radius = frame.size.width / 2
// self.createCircle(origin: origin, radius: radius)
self.addLinesInCircle(origin: origin, radius: radius)
}
func createCircle(origin: CGPoint, radius: CGFloat) {
let path = UIBezierPath()
path.addArc(withCenter: origin, radius: radius, startAngle: 0, endAngle: CGFloat(2 * Double.pi), clockwise: true)
path.close()
UIColor.clear.setFill()
path.fill()
}
func addLinesInCircle(origin: CGPoint, radius: CGFloat) {
let bezier = UIBezierPath()
let incrementAngle: CGFloat = CGFloat.pi / 24
let ratios: [CGFloat] = [3/6, 5/6, 3/6, 1/6, 5/6, 2/6, 4/6, 2/6, 4/6, 4/6, 4/6, 4/6,
3/6, 5/6, 3/6, 1/6, 5/6, 2/6, 4/6, 2/6, 4/6, 4/6, 4/6, 4/6,
3/6, 5/6, 3/6, 1/6, 5/6, 2/6, 4/6, 2/6, 4/6, 4/6, 4/6, 4/6,
3/6, 5/6, 3/6, 1/6, 5/6, 2/6, 4/6, 2/6, 4/6, 4/6, 4/6, 4/6]
for (index, ratio) in ratios.enumerated() {
let point = CGPoint(x: origin.x + cos(CGFloat(index) * incrementAngle) * radius * ratio,
y: origin.y + sin(CGFloat(index) * incrementAngle) * radius * ratio)
if index == 0 {
bezier.move(to: point)
} else {
bezier.addLine(to: point)
}
}
bezier.close()
let layer = CAGradientLayer()
layer.frame = bezier .bounds
layer.colors = [UIColor.red.cgColor,UIColor.blue.cgColor,UIColor.yellow.cgColor ,UIColor.black.cgColor]
let mask = CAShapeLayer()
mask.frame = bezier.bounds
mask.path = bezier.cgPath
mask.fillColor = UIColor.black.cgColor
layer.mask = mask
self.layer.addSublayer(layer)
self.layer.addSublayer(mask)
}
}
let demoView = DemoView(frame: CGRect(x: 0, y: 0, width: 1000, height: 1000))
Here is the result. I need the exact opposite, assign the gradient to the bezier.
(I directly used the xcode playground in order to test)

Answer 1

One option is to use CGGradient along with using the bezier path as a clipping region. No need for layers.
Replace everything after closing the path with:
let gradient = CGGradient(colorsSpace: nil, colors: [UIColor.red.cgColor,UIColor.blue.cgColor,UIColor.yellow.cgColor ,UIColor.black.cgColor] as CFArray, locations: nil)!
let ctx = UIGraphicsGetCurrentContext()!
ctx.saveGState()
// Clip to the path
bezier.addClip()
// Draw the gradient in the clipped region
ctx.drawLinearGradient(gradient, start: CGPoint(x: 0, y: 0), end: CGPoint(x: 0, y: frame.height), options: [])
ctx.restoreGState()