How to write this void objective-c function in swift - ios

Question

I've found code that I want to use in a swift ios app but I'm having trouble writing it the swift way.
-(void) captureOutput:(AVCaptureOutput*)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection*)connection
{
CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer( sampleBuffer );
CGSize imageSize = CVImageBufferGetEncodedSize( imageBuffer );
// also in the 'mediaSpecific' dict of the sampleBuffer
NSLog( #"frame captured at %.fx%.f", imageSize.width, imageSize.height );
}
It's just the function declaration I'm having trouble with, the contents of the function should be easier. I'm not used to the syntax of:
-(void) captureOutput:(AVCaptureOutput*)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection*)connection
My attempt:
I started trying to write it like this but when nothing would autocomplete within the () I realised it was definitely wrong:
func captureOutput(AVCaptureOutput(didOutputSampleBuffer:)) {
}

Answer 1

You can find the correct declaration in the AVCaptureVideoDataOutputSampleBufferDelegate Protocol Reference, where it is declared like this:
optional func captureOutput(_ captureOutput: AVCaptureOutput!,
didOutputSampleBuffer sampleBuffer: CMSampleBuffer!,
fromConnection connection: AVCaptureConnection!)
You wouldn't write optional in your method definition, though:
class MyDelegate: NSObject, AVCaptureVideoDataOutputSampleBufferDelegate {
func captureOutput(captureOutput:AVCaptureOutput,
didOutputSampleBuffer sampleBuffer:CMSampleBuffer,
fromConnection connection:AVCaptureConnection) {
let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)
let imageSize = CVImageBufferGetEncodedSize(imageBuffer)
NSLog("frame captured at %.fx%.f", imageSize.width, imageSize.height)
}
}