add_admin_columns to CPT helper class

// http://wp.tutsplus.com/tutorials/creative-coding/custom-post-type-helper-class/

// call to the class ##
$cpt_tree = new Custom_Post_Type( "tree" ); // singular custom post type title ##

....

$cpt_tree_admin_column_args = array ( // tree admin colums args ##
    'tag'               => true,
    'category'          => true,
);
$cpt_tree->add_admin_columns( $cpt_tree_admin_column_args ); // add admin columns ##


class Custom_Post_Type {

.....

// this code is added inside the main Custom Post Type class
public function add_admin_columns( $args )
    {

        // We need to know the Post Type name again ##
        $name = strtolower( $this->post_type_name );

        // Columns args ##
        $column_args = $args;

        // Default arguments, overwitten with the given arguments
        $args = array_merge(

            // Default
            array(
                'tag'       => true,
                'category'  => false,
            ),

            // Given
            $column_args

        );

        add_filter( 'manage_edit-'.$name.'_columns',
            function() use( $name, $args )
            {
                $new_columns['cb'] = '<input type="checkbox" />';
                $new_columns['title'] = _x(''.ucwords($name).'', 'column name');
                $new_columns['author'] = __('Author');
                if ( $args["category"] === true ) { // add category column ##
                    $new_columns[''.$name.'_category'] = __('Categories');
                }
                if ( $args["tag"] === true ) { // add tag column ##
                    $new_columns[''.$name.'_tag'] = __('Tags');
                }
                $new_columns['thumbnail'] = __('Thumbnail');
                $new_columns['date'] = _x('Date', 'column name');
                return $new_columns;
            }
        , 10, 2 );


        if ( !function_exists('manage_cpt_columns') ) {
        add_action('manage_'.$name.'_posts_custom_column', 'manage_cpt_columns', 10, 2);
        function manage_cpt_columns( $column_name, $id ) {

            global $wpdb, $name, $post;
            #echo ' - C: '.$column_name;
            $name = get_post_type( $post );
            #echo 'N: '.$name;

            switch ( $column_name ) {

            case $name.'_tag':

                $tags = get_the_terms( $id, ''.$name.'_tag' ); // cpt_tag is the custom taxonomy slug
                if ( !empty( $tags ) ) {
                    $out = array();
                    foreach ( $tags as $c )
                        $out[] = "<a href='edit-tags.php?action=edit&taxonomy=".$name."_tag&tag_ID=$c->term_id&post_type=".$name."'> " . esc_html(sanitize_term_field('name', $c->name, $c->term_id, ''.$name.'_tag', 'display')) . "</a>";
                    echo join( ', ', $out );
                } else {
                    echo '';  //No Taxonomy term defined
                }

                break;

            case $name.'_category':

                $tags = get_the_terms( $id, ''.$name.'_category' ); // cpt_category is the custom taxonomy slug
                if ( !empty( $tags ) ) {
                    $out = array();
                    foreach ( $tags as $c )
                        $out[] = "<a href='edit-tags.php?action=edit&taxonomy=".$name."_category&tag_ID=$c->term_id&post_type=".$name."'> " . esc_html(sanitize_term_field('name', $c->name, $c->term_id, ''.$name.'_category', 'display')) . "</a>";
                    echo join( ', ', $out );
                } else {
                    echo '';  //No Taxonomy term defined
                }

                break;

            case 'thumbnail':

                if( function_exists('the_post_thumbnail') ) {
                    #echo the_post_thumbnail( 'admin-list-thumb' );
                } else {
                    echo '';
                }
                break;

                break;

            default:
                break;
            } // end switch
    }}
    }
}