Here’s an example of how we solved this problem:
1. Pass Selected Parent Terms In AJAX
You need a JS hook to filter the AJAX request of the child field, and add a new argument that contains the chosen parent term(s):
<?php
add_action('acf/input/admin_footer', 'support_acf_152814_filter_child_ajax');
function support_acf_152814_filter_child_ajax()
{
global $post;
//areas where this functionality is needed
if (!$post || !isset($post->ID) || get_post_type($post->ID) != 'my_posy_type')
return;
?>
<script type="text/javascript">
(function($){
$(document).ready( function() {
acf.add_filter('select2_ajax_data', function( data, args, $input, field, instance ){
let parent_field_key = '<parent_field_key>'; // Parent Field
let target_field_key = '<child_field_key>'; // Child Field
if( data.field_key == target_field_key ){
let parent = acf.getField(parent_field_key);
if (parent) {
data['parent_terms'] = parent.val(); //This is an array if the parent field is multiselect
}
}
return data;
});
});
})(jQuery);
</script>
<?php
}
2. Filter Taxonomy Query of the Child Terms
Here, you need to catch the argument we introduced above, and modify the query accordingly.
What I do here, is that I get the ids of all children of the selected parents, and I use put them in the ‘include’ option of the terms query:
add_filter('acf/fields/taxonomy/query/key=child_field_key', 'support_acf_152814_child_terms_filter', 10, 3);
function support_acf_152814_child_terms_filter( $args, $field, $post_id ) {
// Check if this is an ajax call
$children_ids = [];
if (wp_doing_ajax()) {
if (isset($_POST['parent_terms'])) {
$parent_terms = $_POST['parent_terms'];
if (is_array($parent_terms) && !empty($parent_terms)) {
foreach ($parent_terms as $parent_id) {
$new_children = get_term_children($parent_id, 'disease_categories');
if (!is_wp_error( $new_children )) {
$children_ids = array_merge($children_ids, $new_children);
}
}
}
$args['include'] = $children_ids;
}
}
return $args;
}
I tested the code above and it works in my case. Please @hube2 let me know if this can be improved further.
