Open Radar

 
MapKit works (quite well) using Key-Value Observing. A common pattern for using MKAnnotations is to implement the MKAnnotation protocol on a data model object so that it provides the required coordinate, etc. 

Common good practice leads to model objects being updated asynchronously, thus making coordinate changes invisible to KVO.

To get around this, updates to coordinate must be made on the main thread, thus linking asynchronous processes to the main thread unnecessarily. Alternatively, a dummy object can be made that parallels the model object - but this obviates some of the benefit of model objects.

A function on the MKMapViewDataSource allows providing the annotation *view* for each annotation added to a map. An analogous function could allow providing an animation block for an annotation, allowing not just simple displacement but selective patterns of motion on maps.

Thanks!