Continuously Redrawing a Path with Updated Data

I am developing an audio visualizer MacOS app, and I want to use Quartz/CoreGraphics to render the time-varying spectrum coordinated with the playing audio. My Renderer code is:

import Cocoa

class Renderer: NSView {

override func draw(_ dirtyRect: NSRect) {
    super.draw(dirtyRect)
    NSColor.white.setFill()
    bounds.fill()
    
    guard let context = NSGraphicsContext.current?.cgContext else {return}

    var x : CGFloat = 0.0
    var y : CGFloat = 0.0

    context.beginPath()
    context.move(to: CGPoint(x: x, y: y))

    for bin in 0 ..< 300 {
        x = CGFloat(bin)
        y = CGFloat(Global.spectrum[bin])
        context.addLine(to: CGPoint(x: x, y: y))
    }
    
    context.setStrokeColor(CGColor( red: 1, green: 0, blue: 0, alpha: 1))
    context.setLineWidth(1.0)
    context.strokePath()

    self.setNeedsDisplay(dirtyRect)
}

}

This draws the path once - using the initial all-zeroes values of the spectrum[] array - and then continues to draw that same all-zeroes line indefinitely. It does not update using the new values in the spectrum[] array. I used a print() statement to verify that the values themselves are being updated, but the draw function does not redraw the path using the updated spectrum values. What am I doing wrong?

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