NavigationSnippets.swift

protocol ImageDelegate{
  func onImageReceived(_ picker: ImagePickerController, didReceiveValue value: UIImage)
  func onCancel(_ picker: ImagePickerController)
}

class TakePictureController : UIViewController, ImageDelegate{
  
  func takePicture(){
    let imagePicker = ImagePickerController()
    imagePicker.delegate  = self//self conforms to ImageDelegate protocol
    //...other setup
    present(imagePicker, animated: true, completion: nil)
  }
  
  func onImageReceived(_ picker: ImagePickerController, didReceiveValue value: UIImage){
      imageView.image = value
      picker.dismiss()
  }
  
  func onCancel(_ picker: ImagePickerController){
    picker.dismiss()
  } 
}