Accessing Samples from Mic in iOS Swift and SwiftUI

It took ages to find out this. All the code I found was incomplete and caused errors like any of the following:

* required condition is false: !IsInternalNode(node)

or

* required condition is false format.sampleRate == hwFormat.sampleRate

or

* required condition is false: IsFormatSampleRateAndChannelCountValid(hwFormat)

or

* required condition is false: [AVAudioEngine.mm:573:AttachNode: (!IsInternalNode(node))]

So here’s my code which came from loads of different places and (through gritted teeth) I used AI. All sources had grains of truth in them but I needed to bring them all together to get a result:

import SwiftUI
import CoreAudio
import AVFoundation

struct ContentView: View {
    // Get an instance of an AudioEngine
    var engine: AVAudioEngine = AVAudioEngine()
    // This is the shared instance that seems to provide all the metadata like frames and sample rate
    var aSession: AVAudioSession = AVAudioSession.sharedInstance()
    // This AudioNode will be used to grab the data from the mic
    @State var inputNode: AVAudioNode?
    // I use this to indicated that the sampling has started and so can adjust UI, etc.
    @State var started: Bool = false
    // Just for demo purposes to output to the screen
    @State var text: String = "--"
    // Bool to indicate the user has granted use of the mic to the app
    @State var granted: Bool = false

    // This will start the sampling
    func start() {
        guard !started && granted else { return }…