Conversion error OBJ-C to Swift 3

Question

I am trying to convert a EZAudio (https://github.com/syedhali/EZAudio) Objective-C Library to Swift 3. I am doing the "EZAudioPlayFileExample" part in it.

Objective-C

- (void)openFileWithFilePathURL:(NSURL*)filePathURL
{
    self.audioFile = [EZAudioFile audioFileWithURL:filePathURL];
    self.filePathLabel.text = filePathURL.lastPathComponent;

    //
    // Plot the whole waveform
    //
    self.audioPlot.plotType = EZPlotTypeBuffer;
    self.audioPlot.shouldFill = YES;
    self.audioPlot.shouldMirror = YES;

    //
    // Get the audio data from the audio file
    //
    __weak typeof (self) weakSelf = self;
    [self.audioFile getWaveformDataWithCompletionBlock:^(float **waveformData,
                                                         int length)
    {
        [weakSelf.audioPlot updateBuffer:waveformData[0]
                          withBufferSize:length];
    }];
}

Swift 3

func openFileWithFilePathURL(filePathURL: NSURL) {
        self.audioFile = EZAudioFile(url: filePathURL as URL!)

        //
        // Plot the whole waveform
        //
        self.plot.plotType = .buffer
        self.plot.shouldFill = true
        self.plot.shouldMirror = true

        //
        // Get the audio data from the audio file
        //
        weak var weakSelf = self
        self.audioFile.getWaveformData(completionBlock: {(_ waveformData: Float, _ length: Int) -> Void in
            weakSelf?.plot.updateBuffer(waveformData[0], withBufferSize: length) // error in this line as Float as no subscript members
        })
    }

I know Float parameter have no subscript members like [0]. But I want to convert the Objective-C code. OR anyone here use this library's Swift version. NOTE: I want the "EZAudioPlayFileExample" in it.

Why you want to convert the library to swift you can use objective C libraries in swift project by using bridging headers — Aravind A R, Jul 25 '17 at 10:35
@AravindAR you are correct I am doing with bridging header. Above code is coming from implementation part (ViewController.m). So I need convert that to Swift — , Jul 25 '17 at 10:39
"I know Float parameter have no subscript members like [0]" In Objective-C, it's `float **waveformData`, notice the two `*`. — Larme, Jul 25 '17 at 11:45
https://stackoverflow.com/questions/833112/what-does-having-two-asterisk-in-objective-c-mean + have a look at the sample method `executeAndReturnError:` (it's an official method in the macOS SDK) and how is it declared in Swift with ` AutoreleasingUnsafeMutablePointer` and related stuff to know how to use it in Swift. — Larme, Jul 25 '17 at 11:53
@AlwinLazar I have added an answer and hope it might help you — Aravind A R, Jul 25 '17 at 13:53

Aravind A R · Accepted Answer · 2017-07-25T13:53:24.233

float **waveformData is actually an unsafemutablepointer. So you have to use unsafemutablepointer in swift 3.0. You can use unsafemutablepointer in swift like

UnsafeMutablePointer<UnsafeMutablePointer<Float>>

You could use like

self.audioFile.getWaveformData(completionBlock: {(_ waveformData: UnsafeMutablePointer<UnsafeMutablePointer<Float>>, _ length: Int) -> Void in
            weakSelf?.plot.updateBuffer(waveformData[0], withBufferSize: length)  
        })

I have just downloaded an older version swift implementation of EZAudio and converted to swift 3.0. It is available at this link
I don't know where this will help you or not but you may build on top of this. You could also refer to this issue being reported on the gitHub page

Conversion error OBJ-C to Swift 3

Objective-C

Swift 3

1 Answers1