Applying gradient layer over a UIBezierPath graph - swift

Question

This is my first time asking a question, so pardon me if it not very thorough.
Basically I am trying to apply a gradient layer on top of a UIBezierPath that is drawn as a graph.
Here is my graph:
Here is the gradient layer I am going for:
Here is what I have tried to draw my graph:
let path = quadCurvedPathWithPoints(points: points)
let shapeLayer = CAShapeLayer()
shapeLayer.path = path.cgPath
shapeLayer.strokeColor = UIColor.blue.cgColor
shapeLayer.fillColor = UIColor.white.cgColor
shapeLayer.position = CGPoint(x: 0, y: 0)
shapeLayer.lineWidth = 1.0
This fills the graph with a blue stroke, obviously, but now I am trying to apply the white to green gradient. The way I am doing it is not working. Here is the result:
Here is the code I am struggling with:
let startColor = UIColor.white.withAlphaComponent(0.5)
let endColor = UIColor.green
let gradient = CAGradientLayer()
gradient.colors = [startColor.cgColor, endColor.cgColor]
gradient.startPoint = CGPoint(x: 0.0, y: 0.5)
gradient.endPoint = CGPoint(x: 1.0, y: 0.5)
gradient.frame = path.bounds
let shapeMask = CAShapeLayer()
shapeMask.path = path.cgPath
gradient.mask = shapeLayer
sparkLineView.layer.addSublayer(gradient)

Answer 1

Here's a little demo that draws a UIBezierPath path using a gradient. You can copy this into a Swift playground.
class GradientGraph: UIView {
override func draw(_ rect: CGRect) {
// Create the "graph"
let path = UIBezierPath()
path.move(to: CGPoint(x: 0, y: frame.height * 0.5))
path.addLine(to: CGPoint(x: frame.width * 0.2, y: frame.height * 0.3))
path.addLine(to: CGPoint(x: frame.width * 0.4, y: frame.height * 0.8))
path.addLine(to: CGPoint(x: frame.width * 0.6, y: frame.height * 0.4))
path.addLine(to: CGPoint(x: frame.width * 0.8, y: frame.height * 0.7))
// Create the gradient
let gradient = CGGradient(colorsSpace: nil, colors: [UIColor.white.cgColor,UIColor.green.cgColor] as CFArray, locations: nil)!
// Draw the graph and apply the gradient
let ctx = UIGraphicsGetCurrentContext()!
ctx.setLineWidth(6)
ctx.saveGState()
ctx.addPath(path.cgPath)
ctx.replacePathWithStrokedPath()
ctx.clip()
ctx.drawLinearGradient(gradient, start: CGPoint(x: 0, y: 0), end: CGPoint(x: frame.width, y: 0), options: [])
ctx.restoreGState()
}
}
let graph = GradientGraph(frame: CGRect(x: 0, y: 0, width: 700, height: 700))