Matt Pfeiffer posted a tutorial "Build an Audio Visualizer Using AudioKit and SwiftUI", and posted his source code here. Unfortunately, it doesn't compile. Another user posted a question describing the problem on the tutorial site, but it remains unanswered. That user points out a couple of simple changes that allow it to compile.
However, the line mic?.setOutput(to: micMixer) in Conductor.swift
produces the fatal run-time error:
Cannot use optional chaining on non-optional value of type ‘AKMicrophone’
Any help in fixing this error would be appreciated.