2018-11-03tip-present一个透明VC

 XLNewCommentViewController *vc = [[XLNewCommentViewController alloc] initWithCallback:^{

    }];

    self.definesPresentationContext = YES;

    UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:vc];

    nav.modalPresentationStyle = UIModalPresentationOverCurrentContext;

    [self.navigationController presentViewController:nav animated:false completion:^{

    }];