Objective-C++ cannot initialize parameter of type id<...> with lvalue of type MyType *__strong even though it conforms to protocol -

i'm trying use avkit in osx objective-c++ application, , have videosource class conforms avcaptureaudiodataoutputsamplebufferdelegate, compiler won't accept parameter of type id<avcapturevideodataoutputsamplebufferdelegate>. error: capture.mm:30:48: cannot initialize parameter of type 'id<avcapturevideodataoutputsamplebufferdelegate>' lvalue of type 'videosource *__strong'

this code:

capture.h

#ifndef threesai_capture_h #define threesai_capture_h  #ifdef __objc__  #import <foundation/foundation.h> #import <avfoundation/avfoundation.h>  @interface videosource : nsobject <avcaptureaudiodataoutputsamplebufferdelegate>  @property avcapturesession *s;  - (id) init;  @end  #endif  void hello();  #endif 

capture.mm

#import "capture.h"  @implementation videosource  - (id) init {     if (self = [super init]) {         self.s = [[avcapturesession alloc] init];         avcapturedevice *camera = [avcapturedevice deviceswithmediatype:avmediatypevideo][0];         nserror *e;         avcaptureinput *camerainput = [avcapturedeviceinput deviceinputwithdevice:camera error:&e];         [self.s addinput:camerainput];          avcapturevideodataoutput *captureoutput = [[avcapturevideodataoutput alloc] init];         captureoutput.alwaysdiscardslatevideoframes = yes;         dispatch_queue_t queue;         queue = dispatch_queue_create("cameraqueue", null);         [captureoutput setsamplebufferdelegate:self queue:queue];//error on line          [self.s addoutput:captureoutput];         [self.s startrunning];     }     return self; }  - (void) captureoutput:(avcaptureoutput *)captureoutput didoutputsamplebuffer:(cmsamplebufferref)samplebuffer fromconnection:(avcaptureconnection *)connection {     nslog(@"asdasd"); }  @end  void hello() {     videosource *v = [[videosource alloc] init]; } 

i'm not sure what's this, seems videosource should of type id<avcaptureaudiodataoutputsamplebufferdelegate>. what's going on?

you using avcapturevideodataoutput, you've declared conformance avcaptureaudiodataoutputsamplebufferdelegate protocol. protocols use same method, can change name of protocol (or adopt both if desire).