URL rewrite and navigation structure for wordpress custom post type

Question

I have created the following custom post types:

• Artists
  • Albums
    • Songs

Songs are children of Albums, Albums are children of Artists.

I am trying to set up a navigation structure that shows this relationship, in the following format: http://www.example.com/artists/alicia-keys/discography/girl-on-fire/brand-new-me. alicia-keys is a post name of type artists, girl-on-fire is a post name for the post type albums & brand-new-me is a post name for the post type Songs.

When someone shortens the url to say, http//www.example.com/artists/alicia-keys/discography it should display albums that belong to Alicia Keys and if you simply type http://www.example.com/albums it shows all albums from all artists. if I have a link within the Artists CPT e.g. 'See all albums', I want it to open a new page which displays all albums belonging to the parent artist

I have the following files:

• single-artists.php
• single-albums.php
• single-songs.php
• archive-artists.php
• archive-albums.php
• archive-songs.php

The question can be broken down as follows:

1. Is there a rewrite rule and/or filter code that I will need to write in functions.php? if so, how do i go about it?

2. do I need to change/rewrite the slug? if so, what do I need to do

3. Will I need additional files to achieve the above link structure? if yes please explain.

Just a note: I am using Wp-types plugin to create the custom post types however, I strongly feel this problem is more of a Wordpress challenge rather than one restricted to a specific plugin. After all, I believe the plugin produces almost the same code that you would get if you were to code the post types from scratch but nonetheless, I have also posted a similar question in their forum. If I get an answer there, I will also supply it here to help anyone else who might face such a problem in the future.

UPDATE: Potential path to solution

After some googling I was able to find a path that I believe will lead to solving the problem. I was able to create the following link structure, which loads all albums for alicia keys :

• example.com/artists/alicia-keys/discography .

The code below is taken from a tutorial by Tareq Hasan and modified for the example. see the original here - http://code.tutsplus.com/articles/custom-page-template-page-based-on-url-rewrite--wp-30564

As the original author of the code states, this requires PHP 5.3.0 and up due to use of PHP anonymous functions.

in functions.php

<?php
 //create a rewrite rule that will append /discography to artists endpoint
 function ex_rewrite(){
  //add_rewrite_rule( 'artists/([^/]+)/discography', 'index.php?artists=$matches[1]&discography=yes', 'top' );
   add_rewrite_rule( 'artists/([^/]+)/discography/([^/]+)/?', 'index.php?album_artist=$matches[1]&discography=yes&albums=$matches[2]', 'top' );
 }
 add_action('init','ex_rewrite');
//register query variable so that wordpress recognizes discography query_var
function ex_query_var($vars){
 $vars[]= 'discography';
 $vars[] = 'album_artist';
 return $vars;
}
 add_filter('query_vars','ex_query_var');
//tell wordpress that when it sees the discography query variable,set/load a template called single-artists-discography.
add_filter( 'template_include', function( $path ) {
if ( get_query_var( 'album_artist' ) && is_singular( 'artists' ) ) {
    return get_template_directory() . '/single-artists.php';
}
if ( get_query_var( 'discography' ) && is_singular( 'artists' ) ) {
    return get_template_directory() . '/single-artists-discography.php';
}
return $path;
});

The single-artists-discography holds the logic of displaying all albums belonging to the specific artist. in this case, it will display all albums that belong to Alicia Keys. This answers part three of the question breakdown above, the need for additional files.

So the challenge narrows down to this:

• How to rewrite an Album's URL to display as example.com/artists/alicia-keys/discography/girl-on-fire.
• How to rewrite a song's URL to display as example.com/artists/alicia-keys/discography/girl-on-fire/brand-new-me

I hope now more knowledgeable developers can now use this as a pointer to help me figure out how to solve the above,as I research more.

Answer 1

In order to rewrite a custom post type's URL, or permalink, you'll need to filter the 'post_type_link', which is run whenever get_permalink() is called, allowing you to change a post's permalink. I've include some guide code below.

It seems like you have a handle on the rewrite rules but let me know if you need more help.

add_filter( 'post_type_link', 'filter_the_post_type_link', 1, 4 );
function filter_the_post_type_link( $post_link, $post, $leavename, $sample ) {

    // Filter the permalink by post type
    switch( $post->post_type ) {

        case 'albums':

            // Build permalink
            $post_link = get_bloginfo( 'url' ) . '/artists/';

            // Get the artist
            $album_artist = ??

            // Add artist to permalink
            $post_link .= "{$album_artist}/";

            // Add album name to permalink
            $post_link .= "discography/{$post->post_name}";

            break;

        case 'songs':

            // Build permalink
            $post_link = get_bloginfo( 'url' ) . '/artists/';

            // Get the artist
            $album_artist = ??

            // Add artist to permalink
            $post_link .= "{$album_artist}/";

            // Get the album
            $album = ??

            // Add album to permalink
            $post_link .= "discography/{$album}/";

            // Add song name to permalink
            $post_link .= "{$post->post_name}";

            break;

    }

    return $post_link;

}

Answer 2

This here is a clarification and addition to Rachel's answer. Combining this together with her code will produce the full solution(I was advised to put this here by a moderator rather than editing the question with an update. I give 100% credit for this answer to Rachel)

<?php
 //rewrite rules for discography, news, albums,songs
 function ex_rewrite(){
 //discography rewrite
 add_rewrite_rule( 'artists/([^/]+)/discography/?$', 'index.php?artists=$matches[1]&discography=yes','top');
 //news
add_rewrite_rule('artists/([^/]+)/news/?$', 'index.php?artists=$matches[1]&news=yes','top');
//album rewrite
add_rewrite_rule( 'artists/([^/]+)/discography/([^/]+)/?$', 'index.php?album_artist=$matches[1]&discography=yes&albums=$matches[2]', 'top' );
//song rewrite
add_rewrite_rule( 'artists/([^/]+)/discography/([^/]+)/([^/]+)/?$', 'index.php?album_artist=$matches[1]&discography=yes&albums=$matches[2]&songs=$matches[3]', 'top' );
 }
 add_action('init','ex_rewrite');
//register query variable so that wordpress recognizes discography query_var as well as other variables you might be using
function ex_query_var($vars){
 $vars[]= 'discography';
 $vars[] = 'album_artist';
 $vars[] = 'news';
 return $vars;
}
 add_filter('query_vars','ex_query_var');
//tell wordpress that when it sees the discography or news variable, redirect to to their respective templates.
add_filter( 'template_include', function( $path ) {
if ( get_query_var( 'discography' ) && is_singular( 'artists' ) ) {
    return get_template_directory() . '/single-artists-discography.php';
    // URL will result in example.com/artists/alicia-keys/discography
}
 if ( get_query_var( 'news' ) && is_singular( 'artists' ) ) {
    return get_template_directory() . '/single-artists-news.php';
  //URL will result in example.com/artists/alicia-keys/news
}
return $path;
});
//Rachel's code starts here......

As for the link in example.com/artists/alicia-keys that will take you to example.com/artists/alicia-keys/discography:

<a href="<?php echo get_permalink($post->ID). 'discography/';?>"> See Alicia Keys' Full Discography</a>

In Rachel's code, there are variables where you need to supply the slugs of the parent posts($album_artist, $album). This is where the method you used to establish the relationships between the post types comes into play. I am using a plugin which provides functionality of establishing relationships as well as extracting parent information using foreign keys.

I felt it is important to note this for those who might wonder what information needs to be supplied for both variables.

Answer 3

It seems you've got the discography rule taken care of. You can generate the rewrite rules for all of your single post types via the rewrite argument when your post types are registered. This may require you to manually register your post types, not sure what level of control that plugin provides. You'll also have to be careful about exactly what order you register the post types in so that your rules cascade from most to least specific. This may be another reason you'll have to manually register your post types.

Artists is the most simple, that will be just:

rewrite => array( 'slug' => 'artists' )

An album would be:

rewrite => array( 'slug' => 'artists/%artist%/discography' )

Lastly, songs would be:

rewrite => array( 'slug' => 'artists/%artist%/discography/%album%' )

You'll then need a post_type_link function which loads the related data and swaps it in place of the %artist% and %album% rewrite tags. I'm not sure how those relationships are stored, so I can't tell you how that will work. You can see a similar example of this function with a taxonomy term on this answer.