UI not updating when called on main thread Swift

Question

I am having a hard time getting my annotation's subtitle to update, I am calling it on the main thread and ensuring that the result is correct.

Can anyone see why it would not be updating?

 let stopAnnotation: UUStopAnnotation = view.annotation as! UUStopAnnotation

        // Else get the stop estimation
        webService?.getStopEstimation(routeId: stopAnnotation.routeId, stopId: stopAnnotation.stopId, completion: { (result) in

            print(result)
            DispatchQueue.main.async(execute: {
                stopAnnotation.subtitle = result
            })

        })

Answer 1

You can't change an annotation in the map. Remove this annotation and replace it with one that has the same coordinates but the new subtitle.