无法调用非功能类型的值＆＃39; [AVAssetTrack]＆＃39;

Question

当我在目标c项目中导入Swift库时，我遇到了这个问题，但它正在使用swift项目。 这是班级。请查看

1. 我通过pod导入库。

2. 然后添加swift桥接文件然后在运行应用程序之后构建然后它给我错误。

3. 以下是问题

代码：

final class FDAudioContext {

/// The audio asset URL used to load the context
public let audioURL: URL

/// Total number of samples in loaded asset
public let totalSamples: Int

/// Loaded asset
public let asset: AVAsset

// Loaded assetTrack
public let assetTrack: AVAssetTrack

private init(audioURL: URL, totalSamples: Int, asset: AVAsset, assetTrack: AVAssetTrack) {
    self.audioURL = audioURL
    self.totalSamples = totalSamples
    self.asset = asset
    self.assetTrack = assetTrack
}

public static func load(fromAudioURL audioURL: URL, completionHandler: @escaping (_ audioContext: FDAudioContext?) -> ()) {
    let asset = AVURLAsset(url: audioURL, options: [AVURLAssetPreferPreciseDurationAndTimingKey: NSNumber(value: true as Bool)])

    guard let assetTrack = asset.tracks(withMediaType: AVMediaType.audio).first else {
        NSLog("FDWaveformView failed to load AVAssetTrack")
        completionHandler(nil)
        return
    }

    asset.loadValuesAsynchronously(forKeys: ["duration"]) {
        var error: NSError?
        let status = asset.statusOfValue(forKey: "duration", error: &error)
        switch status {
        case .loaded:
            guard
                let formatDescriptions = assetTrack.formatDescriptions as? [CMAudioFormatDescription],
                let audioFormatDesc = formatDescriptions.first,
                let asbd = CMAudioFormatDescriptionGetStreamBasicDescription(audioFormatDesc)
                else { break }

            let totalSamples = Int((asbd.pointee.mSampleRate) * Float64(asset.duration.value) / Float64(asset.duration.timescale))
            let audioContext = FDAudioContext(audioURL: audioURL, totalSamples: totalSamples, asset: asset, assetTrack: assetTrack)
            completionHandler(audioContext)
            return

        case .failed, .cancelled, .loading, .unknown:
            print("FDWaveformView could not load asset: \(error?.localizedDescription ?? "Unknown error")")
        }
        completionHandler(nil)
    }
}

Answer 1

xcode 9.3尝试

    public static func load(fromAudioURL audioURL: URL, completionHandler: @escaping (_ audioContext: FDAudioContext?) -> ()) {
    let asset = AVURLAsset(url: audioURL, options: [AVURLAssetPreferPreciseDurationAndTimingKey: NSNumber(value: true as Bool)])

    /// guard let assetTrack = asset.tracks(withMediaType: AVMediaType.audio).first else {
    guard let assetTrack = asset.tracks(withMediaType: AVMediaTypeAudio).first else {
        NSLog("FDWaveformView failed to load AVAssetTrack")
        completionHandler(nil)
        return
    }

Answer 2

我也面临这个问题，并在下面做出改变。

guard let assetTrack = asset.tracks(withMediaType: AVMediaTypeAudio).first else {
    NSLog("FDWaveformView failed to load AVAssetTrack")
    completionHandler(nil)
    return
}

这可能对你有用。

Answer 3

guard let assetTrack = asset.tracks.first else {
            NSLog("FDWaveformView failed to load AVAssetTrack")
            completionHandler(nil)
            return
        }