How do I extract just the post ID of the first item in whatever WP_Query returns?

Question

How do I extract just the post ID of the first item in whatever WP_Query returns? All the examples, answers, and documentation that I have seen dives off into doing things with loops. That's nice, but I just want the first ID. Nothing else. As the plugin will only ever generate a custom post type when there is none, the user should only have one. I need to get the ID of that post.

How do I find a post ID? Is there an easier way to find out if the user has a post available?

This is as far as I have gotten:

$query = new WP_Query( array(
        'author'        => $current_user,
        'post_type'     => 'my_custom_post_type',
        // etc.
) );
$author_posts = new WP_Query( $query );
if( $author_posts->have_posts() ) {
    // They have at least one. Grovey, now what?
}
unset($author_posts);

Answer 1

If you only need the ID of a single post of a custom post type, to see if it exists, I'd suggest just using get_posts() with fields set to ids:

$post_ids = get_posts(
    [
        'numberposts' => 1,
        'author'      => $current_user,
        'post_type'   => 'my_custom_post_type',
        'fields'      => 'ids',
    ]
);

if ( isset( $post_ids[0] ) ) {
    $post_id = $post_ids[0];
}

However, if you have a post type where every user gets 1 post, I'd suggest storing the ID of their post as user meta. Then you don't need to bother with this sort of query:

$post_id = get_user_meta( $current_user, 'the_post_type', true );

Answer 2

If you are trying to get the number of posts the user has authored in your custom post type then you need to do the following:

$post_type = '<YOU_CUSTOM_POST_TYPE_SLUG>';
$user_post_count = count_user_posts( $userid , $post_type );
if ($user_post_count == 0) {
    //Do Something
}