setting columns in admin post_type

Hello,

I am trying to add columns in the admin pod post_type area. I’ve created the “book” pod as a separate table in my database but I am unable to display any value for these 2 fields. Any help? Thx.

Here is the code:

   function setting_column_book( $column ) {    
        $column['ref'] = 'Ref';
        $beginning = array_slice( $column, 0 ,1 );
        $beginning[ 'id' ] = __( 'ID');
        $ending = array_slice( $column, 1 );
        $column = array_merge( $beginning, $ending );
    return $column;
} 
add_filter( 'manage_book_posts_columns', 'setting_column_book' ); 


function custom_value_column( $column, $post_id ) {
    switch ( $column ) {

        case 'ref' :
            echo get_post_meta( $post_id , 'ref' , true );        
            break;

        case 'id' :
            echo get_post_meta( $post_id , 'id' , true ); 
            break;
    }
}
add_action( 'manage_book_posts_column' , '_custom_value_column', 10, 2 );