iOS removing MKMapView overlays not working

Question

I would like to remove all the overlays of my map at one point, and I tried different ways but it never works.

Last try I did [self.mapView removeOverlays:self.mapView.overlays]; and it still doesn't work. Any idea how I can remove those overlays?

Thank you.

UPDATE 1

I have the error: malloc: *** error for object 0x5adc0c0: pointer being freed was not allocated *** set a breakpoint in malloc_error_break to debug

I think I know why, but don't really know how to fix it... Here is the code when I need to draw another line on my mapView:

// Create a c array of points. 
MKMapPoint *pointsArray = malloc(sizeof(CLLocationCoordinate2D) * 2);

// Create 2 points.
MKMapPoint startPoint = MKMapPointForCoordinate(CLLocationCoordinate2DMake(oldLatitude, oldLongitude));
MKMapPoint endPoint = MKMapPointForCoordinate(CLLocationCoordinate2DMake(newLatitude, newLongitude));

// Fill the array.
pointsArray[0] = startPoint;
pointsArray[1] = endPoint;

// Erase polyline and polyline view if not nil.
if (self.routeLine != nil) {
    [_routeLine release];
    self.routeLine = nil;
}

if (self.routeLineView != nil) {
    [_routeLineView release];
    self.routeLineView = nil;
}

// Create the polyline based on the array of points.
self.routeLine = [MKPolyline polylineWithPoints:pointsArray count:2];

// Add overlay to map.
[self.mapView addOverlay:self.routeLine];

// clear the memory allocated earlier for the points.
free(pointsArray);

// Save old coordinates.
oldLatitude = newLatitude;
oldLongitude = newLongitude;

So I release the routeLine object which is the previous overlay. So when I tried to remove it, it crashes because it has already been deallocated.

Here is the code for the mapView delegate for adding overlay views:

- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)overlay
{
    MKOverlayView* overlayView = nil;

    if(overlay == _routeLine) {
        // If we have not yet created an overlay view for this overlay, create it now. 
        if(self.routeLineView == nil) {
            self.routeLineView = [[[MKPolylineView alloc] initWithPolyline:_routeLine] autorelease];

            self.routeLineView.fillColor = [UIColor blueColor];
            self.routeLineView.strokeColor = [UIColor blueColor];

            // Size of the trace.
            self.routeLineView.lineWidth = routeLineWidth;
        }

        overlayView = self.routeLineView;
    }

    return overlayView;
}

If you guys know how I can fix this issue, removing all overlays from my MKMapView it would be awesome!

UPDATE 2

I tried not releasing my routeLine and routeLineView objects and it works now. It seems like there are no leaks too. So now I'm doing this:

// Erase polyline and polyline view if not nil.
if (self.routeLine != nil) {
    //[_routeLine release];
    self.routeLine = nil;
}

if (self.routeLineView != nil) {
    //[_routeLineView release];
    self.routeLineView = nil;
}

Answer 1

When you call removeOverlays:, the map view will release the MKOverlay and MKOverlayView objects.

You hold your own references to these in _routeLine and _routeLineView.

After removeOverlays: is called, your variables will be pointing to already-released memory. When you re-create the polyline, you are over-releasing which then results in a crash.

So remove the release calls:

if (_routeLine != nil) {
    [_routeLine release];  // <-- remove this
    self.routeLine = nil;
}

if (_routeLineView != nil) {
    [_routeLineView release];  // <-- remove this
    self.routeLineView = nil;
}