ios - AVCaptureVideoDataOutputSampleBufferDelegate.CaptureOutput not called -

i have self-developed framework (mysdk), , ios app (myapp) uses mysdk.

inside of mysdk, have class (scanner) in mysdk processes images video output of device camera.

here's sample of code:

scanner.swift

class scanner: nsobject, avcapturevideodataoutputsamplebufferdelegate {      var capturedevice : avcapturedevice?     var captureoutput : avcapturevideodataoutput?     var previewlayer : avcapturevideopreviewlayer?     var capturesession : avcapturesession?      var rootviewcontroller : uiviewcontroller?      func scanimage (viewcontroller: uiviewcontroller)     {         nslog("%@", "scanning begins!")          if (capturesession == nil) { capturesession = avcapturesession() }          rootviewcontroller = viewcontroller;          capturesession!.sessionpreset = avcapturesessionpresethigh          let devices = avcapturedevice.devices()          device in devices {             if (device.hasmediatype(avmediatypevideo)) {                 if(device.position == avcapturedeviceposition.back) {                     capturedevice = device as? avcapturedevice                 }             }         }          if (capturedevice != nil) {             nslog("%@", "beginning session!")              beginsession()         }     }      func beginsession()     {         if (capturesession == nil) { capturesession = avcapturesession() }         if (captureoutput == nil) { captureoutput = avcapturevideodataoutput() }         if (previewlayer == nil) { previewlayer = avcapturevideopreviewlayer() }          let queue = dispatch_queue_create("myqueue", dispatch_queue_serial);          captureoutput!.setsamplebufferdelegate(self, queue: queue)         captureoutput!.videosettings = [kcvpixelbufferpixelformattypekey nsstring: int(kcvpixelformattype_32bgra)]          capturesession!.addinput(try! avcapturedeviceinput(device: capturedevice))         capturesession!.addoutput(captureoutput)          previewlayer = avcapturevideopreviewlayer(session: capturesession)         previewlayer!.frame = rootviewcontroller!.view.layer.frame          rootviewcontroller!.view.layer.addsublayer(previewlayer!)          capturesession!.startrunning()     }      func captureoutput(captureoutput: avcaptureoutput!, didoutputsamplebuffer samplebuffer: cmsamplebufferref!, fromconnection connection: avcaptureconnection!)     {         nslog("%@", "captured!")     } } 

inside myapp, have viewcontroller implements ibaction, in scanner class initialized, , scanimage function triggered.

myapp.m:

- (ibaction)btnscanimage_touchdown:(id)sender {     scanner * scanner = [[scanner alloc] init];      [scanner scanimage:self]; } 

the camera view comes inside of app, captureoutput function never fired, , console contains these 2 lines:

2016-03-07 11:11:45.860 myapp[1236:337377] scanning begins! 2016-03-07 11:11:45.984 myapp[1236:337377] beginning session! 

creating standalone app, , embedding code inside scanner.swift viewcontroller works fine; captureoutput function fires properly.

does have idea doing wrong here?

after trial , error, have found solution problem.

apparently, not creating scanner object class variable, local variable.

once scanner object created class variable, delegate method captureoutput fired properly.