How to group posts and get a mixed posts and groups view?

Question

Let's say i need to implement the following in WordPress :

I have a CPT named 'song' which are single songs from different artists. Sometimes songs may be grouped by albums, but not always.

Then i want to display latest releases on my homepage, like :

LATEST RELEASES

• Song 1
• song 2
• Song 3
• Album 1
  • Song 4
  • Song 7
  • Song 9
• Song 6
• Song 8
• Song 10

etc..

So the rule would be to display all posts, from newest to oldest, but if they belong to a group, show the group instead, using the newest post date in group to sort the group with other posts.

Do you see how to create this in WordPress ? With a CTP + custom taxonomy? Or 2 CPT (1 album, 1 song)?

I have done this in the past using 2 CPT (1 album, 1 song):

• You could add any number of songs to an album (with an ACF
• On save_post action, i was adding a "parent_id" custom field to each children containing...the parent post ID.
• Then i could achieve this with a WP_Query that asked for both CPT, but excluded posts with cusom field "parent_id" set.

But that sounded hacky at the time.. Do you see a better way to handle this behavior ? What if i want to use a taxonomy instead of a CPT ? In term of UX, users would prefer adding tags to songs instead of manually creating an album and adding songs to it.

It feels like a very common pattern yet i can't find the right way to do it :(

Answer 1

A custom taxonomy makes perfect sense - here's hoping I haven't missed something:

$songs = get_posts(
    array(
        'post_type' => 'song',
    )
);

$index = array(); // Build an album_id => songs index
foreach ( $songs as $song ) {
    if ( $albums = get_the_terms( $song->ID, 'album' ) )
        $index[ $albums[0]->term_id ][] = $song;
    else
        $index[ count( $index ) - 1 ][] = $song; // All on it's own. Negative index will not clash with album ID
}

echo '<ul class="songs">';
foreach ( $index as $album_id => $songs ) {
    if ( count( $songs ) > 1 ) // More than one song in this album?
        echo '<li class="album">' . get_term_field( 'name', $album_id, 'album' ) . '<ul>';

    foreach ( $songs as $song )
        echo '<li>' . get_the_title( $song ) . '</li>';

    if ( count( $songs ) > 1 )
        echo '</ul></li>';
}
echo '</ul>';

$index will inherit the order of $songs by however they were queried. When a song belongs to an album, any subsequent songs in that album get added to the stack & will appear in the nested list where the first song is indexed.