EmitterCells not showing in CAEmitterLayer - swift

Question

I can't seem to get the CAEmitterLayer display CAEmitterCells. I add the ConfettiEmitterView in Storyboard and the view is being displayed with a red background as intended. But the cells are not showing. No Errors or warinings either.
The code:
import UIKit
class ConfettiEmitterView: UIView {
override class var layerClass:AnyClass {
return CAEmitterLayer.self
}
func makeEmmiterCell(color:UIColor, velocity:CGFloat, scale:CGFloat)-> CAEmitterCell {
let cell = CAEmitterCell()
cell.birthRate = 10
cell.lifetime = 20.0
cell.lifetimeRange = 0
cell.velocity = velocity
cell.velocityRange = velocity / 4
cell.emissionLongitude = .pi
cell.emissionRange = .pi / 8
cell.scale = scale
cell.scaleRange = scale / 3
cell.contents = roundImage(with: .yellow)
return cell
}
override func layoutSubviews() {
let emitter = self.layer as! CAEmitterLayer
emitter.frame = self.bounds
emitter.masksToBounds = true
emitter.emitterShape = .line
emitter.emitterPosition = CGPoint(x: bounds.midX, y: 0)
emitter.emitterSize = CGSize(width: bounds.size.width, height: 1)
emitter.backgroundColor = UIColor.red.cgColor // Setting the background to red
let near = makeEmmiterCell(color: UIColor(white: 1, alpha: 1), velocity: 100, scale: 0.3)
let middle = makeEmmiterCell(color: UIColor(white: 1, alpha: 0.66), velocity: 80, scale: 0.2)
let far = makeEmmiterCell(color: UIColor(white: 1, alpha: 0.33), velocity: 60, scale: 0.1)
emitter.emitterCells = [near, middle, far]
}
func roundImage(with color: UIColor) -> UIImage {
let rect = CGRect(origin: .zero, size: CGSize(width: 12.0, height: 12.0))
return UIGraphicsImageRenderer(size: rect.size).image { context in
context.cgContext.setFillColor(color.cgColor)
context.cgContext.addPath(UIBezierPath(ovalIn: rect).cgPath)
context.cgContext.fillPath()
}
}
}
Adding a view of type ConfettiEmitterView to the UIViewController in Storyboard should be enough to recreate the issue.

Answer 1

Change
cell.contents = roundImage(with: .yellow)
To
cell.contents = roundImage(with: .yellow).cgImage