MKMapView: how to disable base canvas visibility

- (UIView*) viewToDeactivateInView:(UIView*)view {
    UIView *viewFound = nil;
    if( view && view.subviews && [view.subviews count] > 0 ) {
        for( UIView *currentView in view.subviews ) {
            NSString *className = NSStringFromClass( [currentView class] );
            if( [className isEqualToString:@"VKMapCanvas"] ) {
                viewFound = currentView;
                break;
            }
            else {
                viewFound = [self viewToDeactivateInView:currentView];
                if( viewFound ) {
                    break;
                }
            }
        }
    }
    return viewFound;
}

- (void) baseMapEnableVisibility:(BOOL)isVisible {
    UIView *targetView = [self viewToDeactivateInView:localMapView];
    if( targetView ) {
        NSLog( @"MAP CANVAS: %@", NSStringFromClass([targetView class]) );
        [targetView.layer setOpacity:(isVisible ? 1.0 : 0.0)];
    }
    else {
        NSLog( @"MAP CANVAS NOT FOUND." );
    }
}