Wordpress: insert a custom post type instance as an option for a custom taxonomy

Question

I'm trying to connect a custom post type to a taxonomy defined in an other custom post type.

I'll show you an example. I have a custom post type COURSE, i use this post type to create a class for a university, so in this post type i'll have some custom field (teacher, lesson schedule ecc ecc) and a taxonomy called Teacher.

Teacher is an other custom post type i use to represent teachers working in my university.

Now i would like to create a link between the Teacher instance and the Course, so while i'm creating a new course i will have the list of ALL teachers in the university and i can chose one (or more) from this list.

How can i do that, should i define this list of teachers while i'm registering the taxonomy Teacher? Can you give me some code snippet to create this kind of association?

IMPORTANT: i'm looking for a code answer, i don't need a plugin, i want to learn how to create a code to do that.

Thanks in advance.

Answer 1

Ok, so I'm feeling generous and will add another answer :)

This code will run every time a post is created or updated, and it will add a term to your teacher taxonomy with a name that is the same as the post title.

add_action('save_post', 'my_create_teacher_term_from_post');
function my_project_updated_send_email($post_id){

    /** Ensure that this is not a revision */
    if(wp_is_post_revision($post_id))
        return;
    
    /** Get the name of the teacher that has been added/updated */
    $post_title = get_the_title(post_id);
    
    /** Check to see if a term with the same name as the teacher exists... */
    if(!term_exists($post_title, 'teacher')) :  // It does not...
    
        /** Insert the new term */
        wp_insert_term($post_title, 'teacher');
        
    endif;
    
}

Note - If you only want this action to occur when a post is created, not updated, replace the save_post hook with wp_insert_post.

---

Additional reading

• WordPress action hooks - http://codex.wordpress.org/Plugin_API/Action_Reference

  These will be essential to you going forward, and I fully encourage you to root through the core to see which hooks are available - just be careful!

• The save_post action hook - http://codex.wordpress.org/Plugin_API/Action_Reference/save_post

  Used in the example above, this hook is called everytime a post is created/updated.

• The wp_insert_post action hook - http://codex.wordpress.org/Plugin_API/Action_Reference/wp_insert_post

  You can use this hook instead if you wish, it's only called when a post is updated though, not created. And should you ever need to use both this hook and the save_post hook, note that this one is called after save_post.

• The term_exists function - http://codex.wordpress.org/Function_Reference/term_exists

  This is how you'll see if a term with a name that matches the title of the teacher you've just added already exists.

• The wp_insert_term function - http://codex.wordpress.org/Function_Reference/wp_insert_term

  Finally this is how you acutally create a term progamatically.

Answer 2

I'd suggest that you take a look at the Posts 2 Posts plugin.

This plugin allows you to create a link between posts of any type. For example -

p2p_register_connection_type(array(
    'name' => 'courses_to_teachers',
    'from' => 'course',
    'to' => 'teacher'
));

You'll then have an additional box when editing a post of either type - https://wordpress.org/plugins/posts-to-posts/screenshots/

So if you are adding/editing a course you can link it to multiple teachers, or vice-versa

I have used this in the past, and while it can be a little complicated to start with, there is very good support and I alwasys found the author very good at answering questions posted via the WP support forum.

The Author, Scribu, has his own website related to the plugin that is full of examples and descriptions - http://scribu.net/wordpress/posts-to-posts/

And there is plenty of support on offer via the WP forums - https://wordpress.org/support/plugin/posts-to-posts