   
   
   // return the latest message received for a given measurement string name
-  open func getLatest(_ key:NSString) -> VehicleMeasurementResponse {
-    if let entry = latestVehicleMeasurements[key] {
-      return entry as! VehicleMeasurementResponse
-    }
-    return VehicleMeasurementResponse()
+  open func getLatest(_ key:NSString) -> VehicleMeasurementResponse? {
+    return latestVehicleMeasurements[key]
   }
   
   

  // default callback action for measurement messages not registered above
  fileprivate var defaultMeasurementCallback : TargetAction?
  // dictionary holding last received measurement message for each measurement type
  fileprivate var latestVehicleMeasurements: NSMutableDictionary! = NSMutableDictionary()
  
  // dictionary for holding registered diagnostic message callbacks
  // pairing bus-id-mode(-pid) String with callback action

          rsp.event = event
          
          // capture this message into the dictionary of latest messages
          latestVehicleMeasurements[name] = rsp
          
          // look for a specific callback for this measurement name
          var found=false
