gistfile1.m

@interface MSHidesConferenceRoomsViewController : UIViewController <MRMapViewDelegate>
@property (nonatomic, strong) MRMapView *mapView;
@property (nonatomic, assign) BOOL conferenceHidden;
@property (nonatomic, strong) NSArray *placemarks;
@end

@implementation MSHidesConferenceRoomsViewController

- (id)initWithNibName:(NSString *)name bundle:(NSBundle *)bundle {
    if ((self = [super initWithNibName:name bundle:bundle])) {
        self.edgesForExtendedLayout = UIRectEdgeNone;
        UIBarButtonItem *button1 = [[UIBarButtonItem alloc] initWithTitle:@"Hide ConferenceRooms" style:UIBarButtonItemStylePlain target:self action:@selector(toggle)];
        self.navigationItem.rightBarButtonItems = @[button1];
    }
    return self;
}

#pragma mark - UIViewController

- (void)loadView {
    self.mapView = [[MRMapView alloc] init];
    self.mapView.delegate = self;
    self.mapView.mapKey = [MREditorKey keyForMap:@"13001" app:@"5376006"];
    self.view = self.mapView;
}

#pragma mark - Action

- (void)toggle {
    self.conferenceHidden = !self.conferenceHidden;
    [self reloadAnnotations];
}

#pragma mark - MRMapViewDelegate

- (void)mapViewWillStartLoadingMap:(MRMapView *)mapView {
    self.mapView.showsPlacemarks = YES;
    self.placemarks = nil;
    [self reloadAnnotations];
}

- (void)mapView:(MRMapView *)mapView didLoadPlacemarks:(NSArray *)placemarks {
    self.mapView.showsPlacemarks = NO;
    self.placemarks = placemarks;
    [self reloadAnnotations];
}

#pragma mark - Internal

- (void)reloadAnnotations {
    NSArray *existing = self.mapView.annotations;
    NSMutableArray *annotations = [NSMutableArray array];
    NSMutableArray *toAdd = [NSMutableArray array];
    NSMutableArray *toRemove = [NSMutableArray array];
    for (MRPlacemark *i in self.placemarks) {
        if (![i.type isEqualToString:@"conference_room"] || !self.conferenceHidden) {
            [annotations addObject:i];
        }
    }
    for (id<MRAnnotation> i in annotations) {
        if (![existing containsObject:i]) {
            [toAdd addObject:i];
        }
    }
    for (id<MRAnnotation> i in existing) {
        if (![annotations containsObject:i]) {
            [toRemove addObject:i];
        }
    }
    [self.mapView addAnnotations:toAdd];
    [self.mapView removeAnnotations:toRemove];
}

@end