Fill custom fields when saving custom post types

Question

I have a Custom Post Type called "Report." It has some custom fields, including the name of the place where the post has been written.

I would like that when a user saves (or updates) the post from the admin interface, if he did not fill the place name, the system will fill in automatically on the basis of latitude/longitude (using reverse geocoding).

Which hook should I use?

Answer 1

You would use "save_post" hook. It will look something like this.

add_action( 'save_post', 'populate_empty_place' );

function populate_empty_place( $post_id ) {

    //verify post is not a revision
    if ( !wp_is_post_revision( $post_id )  && get_post_type($post_id) == 'report') {

        // Check for empty place
        // And popluate with your own value     
    }

}