gistfile1.m

    UILabel *label = [UILabel new];
    label.text = locked ? @"🔒" : @"🔓";
    UIBarButtonItem *lockBtn = [[UIBarButtonItem alloc] initWithCustomView:label];
    lockBtn.tintColor = [UIColor redColor];
//    UIBarButtonItem *lockBtn = [[UIBarButtonItem alloc] initWithTitle:title
//                                                                style:UIBarButtonItemStyleBordered
//                                                               target:nil action:nil];
    NSMutableArray *rightBarButtonItems = [self.navigationItem.rightBarButtonItems mutableCopy];
    [rightBarButtonItems insertObject:lockBtn atIndex:0];
    self.navigationItem.rightBarButtonItems = rightBarButtonItems;