iOS 6 でマップアプリの経路を開く

- (void)openMapsWithLatitude:(double)latitude longitude:(double)longitude
{
    // openMapsWithItems が定義されていれば実行
    Class itemClass = [MKMapItem class];
    if (itemClass && [itemClass respondsToSelector:@selector(openMapsWithItems:launchOptions:)]) {
        CLLocation *location = [[CLLocation alloc] initWithLatitude:latitude longitude:longitude];

        // 緯度経度から逆変換して位置情報取得
        CLGeocoder *geocoder = [[CLGeocoder alloc] init];
        [geocoder reverseGeocodeLocation:location completionHandler:^(NSArray *placemarks, NSError *error) {
            MKPlacemark *placemark = [[MKPlacemark alloc] initWithPlacemark:[placemarks objectAtIndex:0]];

            MKMapItem *mapItem = [[MKMapItem alloc] initWithPlacemark:placemark];
            NSArray *mapItems = [NSArray arrayWithObjects:mapItem, nil];
            // 歩いた場合の経路を表示するオプション
            NSDictionary *launchOptions = [NSDictionary dictionaryWithObjectsAndKeys:MKLaunchOptionsDirectionsModeWalking, MKLaunchOptionsDirectionsModeKey, nil];
            [MKMapItem openMapsWithItems:mapItems launchOptions:launchOptions];
        }];
    }
}