So I’ve got a simple object recognition app in iOS. I am trying to create an Interface-Adapter for the machine learning / computer vision like this:

protocol MachineLearningInterface {
    func detectObject(from sampleBuffer: CMSampleBuffer) -> Observable<DetectedObjectEntity>
}
// Either Apple or Google
class AppleMachineLearningAdapter {
    func detectObject(from sampleBuffer: CMSampleBuffer) -> Observable<DetectedObjectEntity> {
        ...
    }
}

class GoogleMachineLearningAdapter {
    func detectObject(from sampleBuffer: CMSampleBuffer) -> Observable<DetectedObjectEntity> {
        ...
    }
}

In the ViewController the input is from this delegate function:

extension ViewController: AVCaptureVideoDataOutputSampleBufferDelegate {
    func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
        viewModel.outputSampleBuffer.accept(sampleBuffer) //viewModel.outputSampleBuffer is a BehaviorRelay
    }
}

Now, I am confused about how to make the UseCase here because obviously the Presentation Layer and the Data Layer is coupled because they need the CMSampleBuffer to function. Is it okay to do this? Because in that case, I also need to use CMSampleBuffer in the UseCase and Entity. But UseCases and Entities shouldn’t know about the layers above them, right?

Thanks.

PS: Maybe I’ll rephrase the question: What if my View/ViewModel use the same object as the Interface-Adapter/Controller (ie.the CMSampleBuffer)? Do I have to map CMSampleBuffer to DTO (say, SampleBufferDTO), then send it to the UseCase (eg. CheckForObjectDetectionUseCase.check(with dto: SampleBufferDTO) -> Observable<DetectedObjectEntity>), then use the Interface-Adapter with the DTO (AppleMachineLearningAdapter.detectObject(_ dto: SampleBufferDTO) -> Observable<DetectedObjectEntity>) in which it will map the DTO back to CMSampleBuffer.

Or just do the whole logic for object detection in the View/ViewModel without having a UseCase in-between?

BTW, I also got the same problem when trying to bind the View/ViewModel to the other layers for a video call feature where the video call services such as Twilio, Agora, etc should’ve been accessed behind a Controller but they are pretty much coupled with the AVFoundation and CallKit from the View.