Problems When Removing Annotations

Question

I am attempting to loop through all of a maps annotations and check to see if it's a MKUserLocation annotation. If it's not I want to remove it so I can add some other ones. I am trying to use the code below but it crashes w /the following error: "Terminating app due to uncaught exception 'NSGenericException', reason: '* Collection <__NSArrayM: 0x1645d0> was mutated while being enumerated."

for(id a in [[self mapview] annotations]) {

     if([a class] != [MKUserLocation class]) {

          [[self mapview] removeAnnotation:a];

     }

}

How can I properly loop through all of the annotations and remove them while still ensuring that the userLocation marker isn't removed.

Answer 1

Try operating on a copy of the annotations array, which should still work.

NSArray *annotationsCopy = [self.mapView.annotations copy];
for(id a in annotationsCopy) {
     if([a class] != [MKUserLocation class]) {
          [[self mapview] removeAnnotation:a];
     }
}
[annotationsCopy release];

If annotations are added to the map view while this is running, they won't be removed.

It looks like the map view is using a mutable array internally, and looping through it while removing objects would put it in an untenable state.