Reply To: Restrict meta value to only be assigned once

• tmgale12

• July 5, 2016 at 10:34 pm

Thanks John,

So I have got this to work now.

I created a taxonomy field and then used the validate_value filter to auto populate the field based on the existing taxonomy that had been selected for post.

I then used a tax_query combined with get_the_terms to populate the terms parameter in the tax_query based on the posts term id.

The only thing that is odd is that the validation message appears in on new page i.e. /wp-admin/post.php as opposed to being on the page.

Below is my code for reference, hopefully this helps anyone that has a similar requirement.

 add_filter('acf/load_value/name=hidden_post_id', 'set_hidden_post_id_value', 10, 3);
function set_hidden_post_id_value($value, $post_id, $field) {
  // set the value of the field to the current post id
  return $post_id;
}

//Auto populate tax field from post terms
add_filter('acf/load_value/name=topic', 'set_topic_value', 10, 3);
function set_topic_value($value, $post_id, $field) {

 // Get term id for current post
  $terms = get_the_terms(get_the_ID(), 'topic');

        if ( $terms && !is_wp_error( $terms )) {
            $term_list = wp_list_pluck( $terms, 'term_id' );
           // set the value of the field to the current term id
          return $term_list;
          }
    }

  add_filter('acf/validate_value/name=top_four_num', 'require_unique', 10, 4);
function require_unique($valid, $value, $field, $input) {

 // Get term id for current post
  $terms = get_the_terms(get_the_ID(), 'topic');
  if ( $terms && !is_wp_error( $terms )) {    
            $term_list = wp_list_pluck( $terms, 'term_id' );          
          }

  if (!$valid) {
    return $valid;
  }
  // get the post id
  // using field key of post id field
  $post_id = $_POST['acf']['field_57765d437d860'];
  // query existing posts for matching value
  $args = array(
    'post_type' => 'knowledge-base',
    'posts_per_page' => 1, // only need to see if there is 1
    'post_status' => 'publish, draft, trash',
    'post__not_in' => array($post_id),
    'meta_query' => array(
      array(
        'key' => $field['name'],
        'value' => $value
      ),
    ),
    'tax_query' => array(
            array(
                'taxonomy' => 'topic',
                'terms'    => $term_list,                                       
            ),
        ),
  );
  $query = new WP_Query($args);
  if (count($query->posts)){
    $valid = 'Value is not unqiue. Please ensure this is selected once.';
  }
  return $valid;
}

Thanks once again John!