The Relationship field creates a very attractive version of the post object field. With a Relationship field, you can select from pages + posts + custom post types. This field is useful for advanced linking to another page / post object.
Creating a Relationship field
The Relationship field contains options to customize your field:
- Post type: You can filter the choices by selecting post types.
- Filter from Taxonomy: You can filter the choices even more by selecting specific taxonomies / categories
- Maximum Posts: You can set the maximum number of posts allowed to be selected. Leave this field blank or set to -1 for infinite selections.
The API will return an array of post objects in the same way that the get_posts function would.
Basic loop (with setup_postdata)
This example shows how to load the selected posts from a relationship field and display them in a list. This example uses a function called
setup_postdata which will override the global $post object and allow functions such as
the_title to target the selected post. When using this function, it is important to reset the post after your loop. http://codex.wordpress.org/Template_Tags/get_posts#Reset_after_Postlists_with_offset
<?php $posts = get_field('relationship_field_name'); if( $posts ): ?> <ul> <?php foreach( $posts as $post): // variable must be called $post (IMPORTANT) ?> <?php setup_postdata($post); ?> <li> <a href="<?php the_permalink(); ?>"><?php the_title(); ?></a> <span>Custom field from $post: <?php the_field('author'); ?></span> </li> <?php endforeach; ?> </ul> <?php wp_reset_postdata(); // IMPORTANT - reset the $post object so the rest of the page works correctly ?> <?php endif; ?>
Basic loop (without setup_postdata)
This example shows how to load the selected posts from a relationship field and display them in a list. This example does not use the above mentioned
setup_postdata function, instead, the
$post->ID is passed to the functions to target the selected post. Please note that some of the function names change to allow for the $post_id parameter such as
the_title() => get_the_title().
<?php $posts = get_field('relationship_field_name'); if( $posts ): ?> <ul> <?php foreach( $posts as $p ): // variable must NOT be called $post (IMPORTANT) ?> <li> <a href="<?php echo get_permalink( $p->ID ); ?>"><?php echo get_the_title( $p->ID ); ?></a> <span>Custom field from $post: <?php the_field('author', $p->ID); ?></span> </li> <?php endforeach; ?> </ul> <?php endif; ?>
Using WP_Query arguments
It is possible to load only the selected post ID’s, instead of the post objects. This way, you can use the ID’s within a WP_Query and specify arguments such as posts_per_page, order and orderby. To learn more about the WP_Query arguments, please read http://codex.wordpress.org/Class_Reference/WP_Query#Parameters.
Note that the get_field function has 2 false parameters. The first param is for the $post_id and is not relevant, but the second one is to tell ACF not to format the value, and return only what is in the DB (array of IDs)
<?php // get only first 3 results $ids = get_field('conference_talks', false, false); $query = new WP_Query(array( 'post_type' => 'conferences', 'posts_per_page' => 3, 'post__in' => $ids, 'post_status' => 'any', 'orderby' => 'rand', )); ?>
It is possible to perform a reverse query on a post (post A) to find all the posts (post B, post C) which have selected it (post A). To learn more about a reverse query, please read this in-depth tutorial: http://www.advancedcustomfields.com/resources/tutorials/querying-relationship-fields/