Reply To: Showing reverse relationships within admin

• cjke7777

• December 16, 2016 at 4:47 pm

Ok so yep it seems like you need a relationship field in both. I’m not totally comfortable with storing the relationship twice – I feel like thats a sleeper-bug waiting to happen.

ie:
– Movie A stores thats it is GenreA, GenreB, and
– GenreA stores (separately) that is has Movie A
– GenreB stores (separately) that is has Movie A

So, as a compromise, for each relation, I nominate one as the relationship owner and only it can edit the relationship. And for the non-relationship owner I have added the following meta box which will list all possible relations.

// Helper to grab all possible post types that could contain relationships
if (! function_exists('get_content_post_types')) {
    function get_content_post_types() {
        return array_merge(
            ['page', 'post'],
            array_values(get_post_types([ '_builtin' => false ]))
        );
    }
}

// Create a query that finds our parent id in the serialised array
if (! function_exists('acf_find_parents')) {
    function acf_find_parents($id, $fields) {
        return new \WP_Query([
            'post_type' => get_content_post_types(),
            'meta_query' => [
                'relation' => 'OR',
                array_map(function($field) use ($id) {
                    return [
                        'key'       => $field,
                        'value'     => '"' .$id. '"',
                        'compare'   => 'LIKE'
                    ];
                }, $fields),
            ]
        ]);
    }
}

And then the usage would be something like:

// Inside the genre page
// This would find all times that this post has existed in anothers relation
acf_find_parents($post->ID, ['music', 'movies', 'books']);

An example of formatting this nicely would be:

// Using laravels collect methods
add_action('add_meta_boxes', function() {
    add_meta_box('genre_relationships', 'Relationships', function($post) {
        collect(acf_find_parents($post->ID, ['music', 'movies'])->posts)
            ->groupBy('post_type')
            ->each(function($type, $key) {
                echo "<h3>{$key}</h3>";
                $type->each(function($related) {
                    echo "<div>{$related->post_title}</div>";
                });
            });
    });
});

This would spit out:

music
song G
song F
movies
movie A
movie C

Again, its a bit of a compromise, but I would prefer this over duplicating the data.

Disclaimer: The query probably should extend to join against the post table to make the post_type is actually a acf field