AudioKit : AKNodeOutputPlot和AKMicrophone不能工作，可能是因为生命周期或MVVM架构决策

Question

在我学习AudioKit的早期，在一个更大的应用程序中，我采纳了标准的建议，即AudioKit should be effectively be a global singleton.我成功地构建了一个非常复杂的原型，而且在世界上一切都很好。

有一次，我开始扩大规模，并接近实际发行版。我们决定采用MVVM作为我们的架构，并且尝试不让一个巨大的AudioKit辛格尔顿来处理我们在应用程序中的音频需求的每一个方面。简而言之，MVVM非常优雅，并且已经明显地清理了我们的代码基础。

与我们的AudioKit结构直接相关，它是这样的：

AudioKit和AKMixer驻留在Singelton实例中，并且具有允许各种视图模型和其他音频模型连接和分离各种节点(AKPlayer、AKSampler等)的公共函数。在我所做的最小测试中，我可以确认这在我对我的AKPlayer模块所做的尝试中是有效的，而且它工作得很好。

我遇到了一个问题，在我的一生中，我无法让AKNodeOutputPlot和AKMicrophone彼此工作，尽管实际的代码实现与我的工作原型是相同的。

我关心的是，我是否做了错误的事情，认为我可以模块化AudioKit以及需要连接到它的各个节点和组件，或者AKNodeOutputPlot是否有我不知道的特殊需求。

下面是我可以提供的最简短的代码片段，而不需要回答这个问题：

AudioKit Singelton (在AppDelegate中称为)：

import Foundation
import AudioKit

class AudioKitConfigurator
{
    static let shared: AudioKitConfigurator = AudioKitConfigurator()

    private let mainMixer: AKMixer = AKMixer()

    private init()
    {
        makeMainMixer()
        configureAudioKitSettings()
        startAudioEngine()
    }

    deinit
    {
        stopAudioEngine()
    }

    private func makeMainMixer()
    {
        AudioKit.output = mainMixer
    }

    func mainMixer(add node: AKNode)
    {
        mainMixer.connect(input: node)
    }

    func mainMixer(remove node: AKNode)
    {
        node.detach()
    }

    private func configureAudioKitSettings()
    {
        AKAudioFile.cleanTempDirectory()
        AKSettings.defaultToSpeaker = true
        AKSettings.playbackWhileMuted = true
        AKSettings.bufferLength = .medium

        do
        {
            try AKSettings.setSession(category: .playAndRecord, with: .allowBluetoothA2DP)
        }

        catch
        {
            AKLog("Could not set session category.")
        }

    }

    private func startAudioEngine()
    {
        do
        {
            try AudioKit.start()
        }
        catch
        {
            AKLog("Fatal Error: AudioKit did not start!")
        }
    }

    private func stopAudioEngine()
    {
        do
        {
            try AudioKit.stop()
        }
        catch
        {
            AKLog("Fatal Error: AudioKit did not stop!")
        }
    }
}

麦克风组件：

import Foundation
import AudioKit
import AudioKitUI

enum MicErrorsToThrow: String, Error
{
    case recordingTooShort          = "The recording was too short, just silently failing"
    case audioFileFailedToUnwrap    = "The Audio File failed to Unwrap from the recorder"
    case recorderError              = "The Recorder was unable to start recording."
    case recorderCantReset          = "In attempt to reset the recorder, it was unable to"
}

class Microphone
{
    private var mic:            AKMicrophone    = AKMicrophone()
    private var micMixer:       AKMixer         = AKMixer()
    private var micBooster:     AKBooster       = AKBooster()
    private var recorder:       AKNodeRecorder!
    private var recordingTimer: Timer

    init()
    {
        micMixer = AKMixer(mic)
        micBooster = AKBooster(micMixer)
        micBooster.gain = 0
        recorder = try? AKNodeRecorder(node: micMixer)

        //TODO: Need to finish the recording timer implementation, leaving blank for now
        recordingTimer = Timer(timeInterval: 120, repeats: false, block: { (timer) in

        })

        AudioKitConfigurator.shared.mainMixer(add: micBooster)
    }

    deinit {
//      removeComponent()
    }

    public func removeComponent()
    {
        AudioKitConfigurator.shared.mainMixer(remove: micBooster)
    }

    public func reset() throws
    {
        if recorder.isRecording
        {
            recorder.stop()
        }
        do
        {
            try recorder.reset()
        }
        catch
        {
            AKLog("Recorder can't reset!")
            throw MicErrorsToThrow.recorderCantReset
        }
    }

    public func setHeadphoneMonitoring()
    {
        // microphone will be monitored while recording
        // only if headphones are plugged
        if AKSettings.headPhonesPlugged {
            micBooster.gain = 1
        }
    }

    /// Start recording from mic, call this function when using in conjunction with a AKNodeOutputPlot so that it can display the waveform in realtime while recording
    ///
    /// - Parameter waveformPlot: AKNodeOutputPlot view object which displays waveform from recording
    /// - Throws: Only error to throw is from recorder property can't start recording, something wrong with microphone. Enum is MicErrorsToThrow.recorderError
    public func record(waveformPlot: AKNodeOutputPlot) throws
    {
        waveformPlot.node = mic
        do
        {
            try recorder.record()
//          self.recordingTimer.fire()
        }
        catch
        {
            print("Error recording!")
            throw MicErrorsToThrow.recorderError
        }
    }

    /// Stop the recorder, and get the recording as an AKAudioFile, necessary to call if you are using AKNodeOutputPlot
    ///
    /// - Parameter waveformPlot: AKNodeOutputPlot view object which displays waveform from recording
    /// - Returns: AKAudioFile
    /// - Throws: Two possible errors, recording was too short (right now is 0.0, but should probably be like 0.5 secs), or could not retrieve audio file from recorder, MicErrorsToThrow.audioFileFailedToUnwrap, MicErrorsToThrow.recordingTooShort
    public func stopRecording(waveformPlot: AKNodeOutputPlot) throws -> AKAudioFile
    {
        waveformPlot.pause()
        waveformPlot.node = nil

        recordingTimer.invalidate()
        if let tape = recorder.audioFile
        {
            if tape.duration > 0.0
            {
                recorder.stop()
                AKLog("Printing tape: CountOfFloatChannelData:\(tape.floatChannelData?.first?.count) | maxLevel:\(tape.maxLevel)")
                return tape
            }
            else
            {
                //TODO: This should be more gentle than an NSError, it's just that they managed to tap the buttona and tap again to record nothing, honestly duration should probbaly be like 0.5, or 1.0 even. But let's return some sort of "safe" error that doesn't require UI
                throw MicErrorsToThrow.recordingTooShort
            }
        }
        else
        {
            //TODO: need to return error here, could not recover audioFile from recorder
            AKLog("Can't retrieve or unwrap audioFile from recorder!")
            throw MicErrorsToThrow.audioFileFailedToUnwrap
        }
    }
}

现在，在我的VC中，AKNodeOutputPlot是一个关于Storybard的视图，并通过IBOutlet连接起来。它呈现在屏幕上，它是按我的喜好风格，它绝对是连接和工作。在VC/VM中，还有我的Microphone组件的一个实例属性。我的想法是，在记录时，我们将nodeOutput对象传递给ViewModel，然后ViewModel调用Microphone的record(waveformPlot: AKNodeOutputPlot)函数，然后waveformPlot.node = mic就足以将它们连接起来。遗憾的是，情况并非如此。

查看：

class ComposerVC: UIViewController, Storyboarded
{
    var coordinator: MainCoordinator?
    let viewModel: ComposerViewModel = ComposerViewModel()

    @IBOutlet weak var recordButton: RecordButton!
    @IBOutlet weak var waveformPlot: AKNodeOutputPlot! // Here is our waveformPlot object, again confirmed rendering and styled

    // MARK:- VC Lifecycle Methods
    override func viewDidLoad()
    {
        super.viewDidLoad()

        setupNavigationBar()
        setupConductorButton()
        setupRecordButton()
    }

    func setupWaveformPlot() {
        waveformPlot.plotType = .rolling
        waveformPlot.gain = 1.0
        waveformPlot.shouldFill = true
    }

    override func viewDidAppear(_ animated: Bool)
    {
        super.viewDidAppear(animated)

        setupWaveformPlot()

        self.didDismissComposerDetailToRootController()
    }

    // Upon touching the Record Button, it in turn will talk to ViewModel which will then call Microphone module to record and hookup waveformPlot.node = mic
    @IBAction func tappedRecordView(_ sender: Any)
    {
        self.recordButton.recording.toggle()
        self.recordButton.animateToggle()
        self.viewModel.tappedRecord(waveformPlot: waveformPlot)
        { (waveformViewModel, error) in
            if let waveformViewModel = waveformViewModel
            {
                self.segueToEditWaveForm()
                self.performSegue(withIdentifier: "composerToEditWaveForm", sender: waveformViewModel)
                //self.performSegue(withIdentifier: "composerToDetailSegue", sender: self)
            }
        }
    }

ViewModel：

import Foundation
import AudioKit
import AudioKitUI

class ComposerViewModel: ViewModelProtocol
{

//MARK:- Instance Variables
var recordingState: RecordingState

var mic:            Microphone                      = Microphone()

init()
{
    self.recordingState = .readyToRecord
}


func resetViewModel()
{
    self.resetRecorder()
}

func resetRecorder()
{
    do
    {
        try mic.reset()
    }
    catch let error as MicErrorsToThrow
    {
        switch error {
        case .audioFileFailedToUnwrap:
            print(error)
        case .recorderCantReset:
            print(error)
        case .recorderError:
            print(error)
        case .recordingTooShort:
            print(error)
        }
    }
    catch {
        print("Secondary catch in start recording?!")
    }
    recordingState = .readyToRecord
}

func tappedRecord(waveformPlot: AKNodeOutputPlot, completion: ((EditWaveFormViewModel?, Error?) -> ())? = nil)
{
    switch recordingState
    {
    case .readyToRecord:
        self.startRecording(waveformPlot: waveformPlot)

    case .recording:
        self.stopRecording(waveformPlot: waveformPlot, completion: completion)

    case .finishedRecording: break
    }
}

func startRecording(waveformPlot: AKNodeOutputPlot)
{

    recordingState = .recording
    mic.setHeadphoneMonitoring()
    do
    {
        try mic.record(waveformPlot: waveformPlot)
    }

    catch let error as MicErrorsToThrow
    {
        switch error {
        case .audioFileFailedToUnwrap:
            print(error)
        case .recorderCantReset:
            print(error)
        case .recorderError:
            print(error)
        case .recordingTooShort:
            print(error)
        }
    }
    catch {
        print("Secondary catch in start recording?!")
    }
}

我很高兴提供更多的代码，但我只是不想压倒他们的时间无论如何。逻辑似乎是合理的，我只是觉得我遗漏了一些显而易见的东西，或者是对AudioKit + AKNodeOutputPlot + AKMicrohone的完全误解。

任何想法都是欢迎的，谢谢！

Answer 1

编辑 AudioKit 4.6修复了所有问题！高度鼓励AudioKit的MVVM/模块化为您的项目！

====

所以经过大量的实验。我得出几个结论：

1. 在一个单独的项目中，我引入了我的AudioKitConfigurator和Microphone类，初始化了它们，并将它们连接到AKNodeOutputPlot上，它运行得完美无缺。
2. 在我的大型项目中，无论我做什么，我都不能让相同的类工作。

现在，我回到一个旧的构建，慢慢地添加组件，直到它再次崩溃，并将逐个更新体系结构，因为这个问题太复杂了，并且可能正在与其他库交互。我还将评级从AudioKit 4.5.6降至AudioKit 4.5.3。

这不是一个解决办法，而是目前唯一可行的解决办法。好消息是，用MVVM架构格式化AudioKit是完全可能的。