Check if Wordpress loop has posts - wordpress

Question

I have a custom loop with posts which are added from the custom meta field checkbox. Only if the checkbox is checked, then the post is being added to the loop. I have a container that holds that loop. What i want to do is to check if that loop got any posts and if it is empty - just hide that container. Because otherwise when the loop is empty the container is remaining on the page:
<div>
<ul>
</ul>
</div>
This is the loop:
<?php
/* Slider ------- */
$slider = new WP_Query('showposts=-1');
if ( $slider->have_posts() ):
?>
<div>
<ul>
<?php while ( $slider->have_posts() ) : $slider->the_post(); ?>
<?php if ( get_post_meta($post->ID, "mf_homeslider", true) == 'slider_on' ){ // Check if post was added to slider ?>
<li>
<?php if (has_post_thumbnail()) { ?>
<a href="<?php the_permalink(); ?>">
<?php the_post_thumbnail('large'); ?>
</a>
<?php } ?>
<div>
<?php get_template_part('includes/post_meta'); ?>
<h2>
<?php the_title(); ?>
</h2>
</div>
</li>
<?php } ?>
<?php endwhile; ?>
</ul>
</div>
<?php
endif;
wp_reset_query();
?>
Thank you in advance for your help.

Answer 1

You should filter your query by the custom field (see details here), it could also improve performance (an SQL condition vs. a while-if loop). After that, have_posts() returns whether the loop contains any posts.
So instead of
$slider = new WP_Query('showposts=-1');
use
$slider = new WP_Query(array(
'meta_key' => 'mf_homeslider',
'meta_value' => 'slider_on',
'posts_per_page' => -1)
);
and there's no further need for if ( get_post_meta(...
(showposts is deprecated, use posts_per_page instead).
Note: you are mixing braces and if-endif style, the latter would be much readable when nesting.