Setting Track ID

问题

I am having trouble with setting the track id when i set up my input parameters for my audioMix. How do i set the trackId? I have tried it this way also params.trackID(track2.trackID) but that gives me this error CMPersistantTrackID -> $T4 is not identical to CMPersistantTrackID. I am trying to translate this line [audioInputParams setTrackID:[track trackID]]; from https://developer.apple.com/library/ios/qa/qa1716/_index.html

Error When i run code below:

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSArrayM trackID]: unrecognized selector sent to instance 0x7f98c34cbfc0'

Code:

        let type = AVMediaTypeAudio
        let asset1 = AVURLAsset(URL: beatLocationURL, options: nil)
        let arr2 = asset1.tracksWithMediaType(type)
        let track2 = arr2.last as AVAssetTrack


        let asset = AVURLAsset(URL: vocalURL, options:nil)
        let arr3 = asset.tracksWithMediaType(type)
        let track3 = arr3.last as AVAssetTrack



        var trackParams = NSMutableArray()

        let params = AVMutableAudioMixInputParameters(track:track2)
        params.setVolume(0.0, atTime:kCMTimeZero)
        params.trackID = track2.trackID <--- this line 
        trackParams.addObject(params)

        let params1 = AVMutableAudioMixInputParameters(track:track3)
        params1.setVolume(1.0, atTime: kCMTimeZero)
        params1.trackID = track3.trackID <-- this line also
        trackParams.addObject(params1)

        let mix = AVMutableAudioMix()
        mix.inputParameters = [trackParams]

来源：https://stackoverflow.com/questions/27165480/setting-track-id