column values not showing after merging two custom post types

Question

So i have 2 post types 'loads' and 'invoices'. Invoices is also used to show loads posts. I need not Invoices posts at all.

What I have Done: I used this code to show loads posts on Invoice page.

add_action( 'pre_get_posts', 'join_cpt_list_wspe_113808' );

function join_cpt_list_wspe_113808( $query ) 
{
    // If not backend, bail out
    if( !is_admin() )
        return $query;

    // Detect current page and list of CPTs to be shown in Dashboard > invoice > Edit screen
    global $pagenow;
    $cpts = array( 'loads' );

    if( 'edit.php' == $pagenow && ( get_query_var('post_type') && 'invoices' == get_query_var('post_type') ) ){
        //set post type
        $query->set( 'post_type', $cpts );
    
        //Get original meta query
        $meta_query = (array)$query->get('meta_query');

        // show loads that are sent to invoice
        $meta_query[] = array(
                'key'     => 'load_status',
                'value'   => 'complete',
                'compare' => '=',
        );    

        // Set the meta query to the complete, altered query
        $query->set('meta_query',$meta_query);
    }
    return $query;
}

What I want:

On Invoice listing page, column values are not being shown. See screenshot:

I am trying this code to get values:

 function invoice_columns ( $columns ) {
     //unset($columns['title']);
     unset($columns['date']);
     
   return array_merge ( $columns, array ( 
     'company' => __ ( 'Company' ),
     'invoice'   => __ ( 'Invoice #' ) ,
     'reference'   => __ ( 'Reference' ) ,
     'delivery_date'   => __ ( 'Delivery Date' ) ,
     'sent_on'   => __ ( 'Sent On' ) ,
     'invoice_date'   => __ ( 'Invoice Date' ) ,
     'due_date'   => __ ( 'Due Date' ) ,
     'invoice_total'   => __ ( 'Invoice Total' ) ,
     'balance'   => __ ( 'Balance' ) 
   ) );
 }
add_filter ( 'manage_invoices_posts_columns', 'invoice_columns' );
 
function invoice_custom_column($column, $post_id){
    echo $column;
    echo $post_id;
    
    
}
add_action ( 'manage_invoices_posts_custom_column', 'invoice_custom_column', 10, 2 );

Please give your solutions.

Answer 1

The correct action hook for printing custom column content is manage_loads_posts_custom_column, not manage_invoices_posts_custom_column (tested). This is because the row is itself for a loads post type, and not an invoices post type. Because you're on the page for invoices, the filter to add columns works with invoices.

Tested:

add_action( 'manage_loads_posts_custom_column', 'invoice_custom_column', 10, 2 );

I received an error when setting the post_type parameter to an array, so I set to loads as a string. Additionally, pre_get_posts is an action, not a filter, so the return $query is not needed.