Reset postdata not working on WP_Query in functions.php

Question

I'm running a WP_Query in my functions.php, so I can easily access some ACF-fields in my code without having to run that query on every page.

However, the loop changes the post ID to the CPT I'm calling with the WP_Query. This is of course known behavior, so normally I'd just add a wp_reset_postdata() to my query to continue with the page's or post's original ID.

However, no matter where I reset the postdata in my query, it doesn't get reset. A temporary, not so pretty, solution I have found is adding wp_reset_postdata(); after I call the function in my page-file. This fixes it, but isn't very pretty and partially beats the purpose of using the function.

Here's my function:

function get_root_project_value( $meta_key ) {
    $args = array(
      'post_type'         => 'slug',
      'posts_per_page'    => -1,
      'meta_query'    => array(
        array(
            'key'       => 'project_is_root_project',
            'value'     => '1',
        ),
      )
    );
    $project = new WP_Query( $args );

    if ( $project->have_posts() ) {
        while ( $project->have_posts() ) { $project->the_post();
            
            if($meta_key) {
                $meta_value = get_field($meta_key, get_the_id());

                if($meta_value) {
                    return $meta_value;
                } else {
                    return false;
                }
            }
        }
        
        wp_reset_postdata();            
    } else {
        return false;
    }

}

And this is how I use it in my code: $longitude = get_root_project_value('project_longitude');

This will set my current page's ID to the root_project ID, so to reset that (since the wp_reset_postdata() in the function doesn't do that), I add wp_reset_postdata(); just after I set $longitude.

Is there a way to reset the postdata in the function, instead on every single page I use the function?

Answer 1

You don't need to modify the global current post, just use the get_posts() function instead of WP_Query().

function get_root_project_value( $meta_key ) {
    if ( empty( $meta_key ) ){
        return false;
    }

    $args = array(
        'post_type'      => 'slug',
        'meta_query'     => array(
            array(
                'key'   => 'project_is_root_project',
                'value' => '1',
            ),
        ),
        'posts_per_page' => 1,      // If you want only one result, set to 1 instead of -1
        'fields'         => 'ids',  // To get only ids. No need more
    );
    $project_ids = get_posts( $args );
    if ( !empty($project_ids) ){
        foreach ( $project_ids as $project_id ) {
            return get_field( $meta_key, $project_id );
        }
    }
    return false;
}