gistfile1.m

// returns a MKCoordinateRegion that encompasses an array of MKAnnotations

- (MKCoordinateRegion)regionForAnnotations:(NSArray *)annotations {
    
    CLLocationDegrees minLat = 90.0;
    CLLocationDegrees maxLat = -90.0;
    CLLocationDegrees minLon = 180.0;
    CLLocationDegrees maxLon = -180.0;
    
    for (id <MKAnnotation> annotation in annotations) {
        if (annotation.coordinate.latitude < minLat) {
            minLat = annotation.coordinate.latitude;
        }		
        if (annotation.coordinate.longitude < minLon) {
            minLon = annotation.coordinate.longitude;
        }		
        if (annotation.coordinate.latitude > maxLat) {
            maxLat = annotation.coordinate.latitude;
        }		
        if (annotation.coordinate.longitude > maxLon) {
            maxLon = annotation.coordinate.longitude;
        }
    }
    //change borders to show all annotations 
    maxLat += 0.01;
    minLat -= 0.01;
    maxLon += 0.01;
    minLon -= 0.01;
    MKCoordinateSpan span = MKCoordinateSpanMake(maxLat - minLat, maxLon - minLon);
    
    CLLocationCoordinate2D center = CLLocationCoordinate2DMake((maxLat - span.latitudeDelta / 2), maxLon - span.longitudeDelta / 2);
    
    return MKCoordinateRegionMake(center, span);
}