How to add "supports" parameter for a Custom Post Type?

Question

Is there a way to add support for a custom feature for a custom post type, after it has been created?

I know how to create a custom post type using register_post_type(), and how to use the supports parameter to specify what the CPT should support;

'supports' => array( 'title', 'editor', 'author', 'thumbnail', 'excerpt' ,'headway-seo') 

But for the situations when the CPT is being registered by a plugin or theme, is there a way to 'inject' support elements (manipulate the support array) of the CPT after it has been registered, using a WP hook/filter?

Answer 1

Yes, there's a function called add_post_type_support

Hook into init -- late, after the post types have been created -- and add support.

Adding support for excerpts to pages for instance:

<?php
add_action('init', 'wpse70000_add_excerpt', 100);
function wpse70000_add_excerpt()
{
    add_post_type_support('page', 'excerpt');
}

Answer 2

An alternative approach is to hook into register_post_type_args and update the supports array.

This is particularly useful if you have third-party plugins that hook into the CPT arguments to display content.

function wpse70000_add_author_metabox_to_cpt_book( $args, $post_type ) {
    if ($post_type != 'POST_TYPE_NAME') // set post type
        return $args;
    $args['supports'] = array( 'author' ); // set the 'supports' array
    return $args;
}

add_filter( 'register_post_type_args', 'wpse70000_add_author_metabox_to_cpt_book', 10, 2 );