Save ACF relationship (name) value to ACF text field

• albertvisuals

• July 30, 2021 at 5:47 am

I try to achieve the following. I have two post types, “projects” & “kuenstlerinnen” (artists) Within the post type “projects”, there’s an ACF relationship field setup, connecting these two to together → “project_to_kunstlerin”

The post-type “künstlerinnen” (Artists) contains two ACF text fields: first-name (“artist_vorname”) & Last- or Group-Name (“artist_nachname”). There is a code snippet running, which saves both fields to the title → “artist_vorname””artist_nachname”

I know would like to have a hidden text field within the projects post type, which is automatically populated with the first value of the “project_to_kunstlerin” field. It should only use the last name field. The reason I try to get this to work, is that I can order by this hidden field, so I get the posts ordered by the last name of the artist.

So far I come up with the following code-snippet:

<?php

//Make special artist field autosave for sorting
function write_artist_name_to_hidden( $post_id ) {
    $post_type = 'projects'; //custom post type for events
  
    //Check if we are saving correct post type
    if( get_post_type( $post_id ) != $post_type)
      return;
  
    //Check it's not an auto save routine
    if( defined('DOING_AUTOSAVE') && DOING_AUTOSAVE ) 
      return;
    
    // get the artist id  of the post. Note this is in a relationship field
    $nameofartist = get_post_field ('project_to_kunstlerin', $post);
    
  
    // update the artist value 
    update_field( 'project_kunstlerin_nach_name_sort', $nameofartist, $post_id );
  }
  add_action('save_post', 'write_artist_name_to_hidden');

In the backend, it now populates the destination ACF field with:

One artist: “[“37″]” Two artists: [“37″,”38”]

These are the IDs.

How can I get another value there instead of the post id?

In theory, it must be something like:

Check with IDs are in the “project_to_kunstlerin” relationship field.
Take the first ID.
Look up, which value is stored in “artist_nachname” of ID in post type “kuenstlerinnen”
Maybe anybody of you has an idea how to get this to work? Your help is highly appreciated!

• John Huebner

• August 4, 2021 at 4:17 pm

1) change your filter to an acf/save_post filter with priority > 10 ensure that values are saved to the DB before you try using them.

2) Get the value of the relationhip field, unformatted, from the project post being saved.

$kuenstlerinnen_id = get_field ('project_to_kunstlerin', $post_id, false);

The above value could be an array

if (is_array(kuenstlerinnen_id)) {
  $kuenstlerinnen_id = kuenstlerinnen_id[0];
}

get the last name field from the other post

$artist_nachname = get_field('artist_nachname', $kuenstlerinnen_id;

update the field on the project with this value

update_field('project_kunstlerin_nach_name_sort', $artist_nachname, $post_id);

• albertvisuals

• August 7, 2021 at 4:16 pm

Hello John!

Thanks very much for your help!

I have tried to set up a function with your changes as follows:

<?php

//Make special artist field autosave for sorting
function write_artist_name_to_hidden( $post_id ) {

//Get the value of the relationhip field, unformatted, from the project post being saved.
$kuenstlerinnen_id = get_field ('project_to_kunstlerin', $post_id, false);
//The above value could be an array
if (is_array('kuenstlerinnen_id')) {
    $kuenstlerinnen_id = kuenstlerinnen_id[0];
  }

  //get the last name field from the other post

  $artist_nachname = get_field('artist_nachname', $kuenstlerinnen_id);
//update the field on the project with this value

update_field('project_kunstlerin_nach_name_sort', $artist_nachname, $post_id);

  }
  add_action('acf/save_post', 'write_artist_name_to_hidden', 11);

Sadly I am doing something wrong here, as get several warnings when I try to update a post:
Warning: Illegal offset type in isset or empty in /Users/sebastianalbert/Local Sites/fotohof-calling/app/public/wp-content/plugins/advanced-custom-fields-pro/includes/local-meta.php on line 195

Warning: Illegal offset type in isset or empty in /Users/sebastianalbert/Local Sites/fotohof-calling/app/public/wp-content/plugins/acf-extended/includes/core/meta.php on line 168

Warning: Illegal offset type in isset or empty in /Users//Local Sites/fotohof-calling/app/public/wp-content/plugins/advanced-custom-fields-pro/includes/local-meta.php on line 195

Warning: Illegal offset type in isset or empty in /Users//Local Sites/fotohof-calling/app/public/wp-content/plugins/acf-extended/includes/core/meta.php on line 168

Warning: Cannot modify header information – headers already sent by (output started at /Users//Local Sites/fotohof-calling/app/public/wp-content/plugins/advanced-custom-fields-pro/includes/local-meta.php:195) in /Users//Local Sites/fotohof-calling/app/public/wp-includes/pluggable.php on line 1340

Warning: Cannot modify header information – headers already sent by (output started at /Users//Local Sites/fotohof-calling/app/public/wp-content/plugins/advanced-custom-fields-pro/includes/local-meta.php:195) in /Users//Local Sites/fotohof-calling/app/public/wp-includes/pluggable.php on line 1343

Do you have any idea what I am doing wrong here? I am pretty new to the php stuff.
Thanks again for your help!

• John Huebner

• August 9, 2021 at 9:55 am

There is nothing in the code posted that should cause the errors your are getting.

• albertvisuals

• August 10, 2021 at 7:28 am

That is strange.
I am using advanced scripts for my code snippets. As soon as I activate the script above, the error is there (when I save a post). When I deactivate the script, the error is gone.