Add filter to acf relationship field

Question

I am using wordpress 4.9.7 and I am using advanced custom fields 4.4.12.

In my backend I have a post type that is called coins, which has a relationship field called related_coins and a text-field, which is called algorithm. Basically my relationship field creates a relationship to the custom post type products. So product can have a relationship with several coins.

I currently only can filter by post type. However, I would like to filter by the custom field algorithm of the post type coin.

I tried the following:

function graphic_card_products_query( $args, $field, $post_id ) {

    $args['meta_query'] = array(
        array(
        'key' => 'algorithm', // name of custom field
        'value' => 'related_coins',
        'compare' => 'LIKE'
        )
    )

    // return
    return $args;

}

// filter for every field
add_filter('acf/fields/relationship/query/name=related_coins', 'graphic_card_products_query', 10, 3);

Basically I am trying to get a list of all values that the custom field algorithm has and hand it as a filter option back to the relationship field related_coin.

Currently I do not get anything back.

Any suggestions what I am doing wrong?

Answer 1

I have tested this, using your code as a base, and I can confirm it works for me. I'll detail what I did.

First, you may have spotted it, but you are missing a semicolon after your meta_query. So I fixed that.

$args['meta_query'] = array(
    array(
    'key' => 'algorithm', // name of custom field
    'value' => 'related_coins',
    'compare' => 'LIKE'
    )
); // <-- this one!

Next, I made sure that the field I was filtering was indeed a 'Relationship' field, not any of the other 'relational' fields types (Post Object, Links, Taxonomy, for example). They have their own filters (ACF Reference: Filters)

Lastly, I confirmed that the meta_query was correct and what I was expecting. So your meta_query is looking for products with the custom field 'algorithm' and a value of 'related_coins'. (It may well be correct, but make sure the value you want is 'related_coins' as that sounds rather like a key, not a value). You're then using the LIKE operator which will match values with 'related_coins' contained within the value. For example, it will match '123_related_coins' and 'related_coins_123', as well as just 'related_coins'.

As I said, this may be what you want, but just understand that is what the meta query means.

Hope this helps!