I add multiple fields with
$view->addHandler($view->current_display, 'field', 'views', 'nothing', array(
'label' => 'My field',
'type' => 'textfield',
'alter' => array('text' => 'My field text'),
'element_class' => 'my-field',
'element_default_classes' => 0,
'group_rows' => TRUE
), 'my_field');
this works fine but i can't find a way to alter it, because the result data in pre_render, post_render, post_execute doesn't include these field only has entity fields which can be changed with
$result->_entity->set('title', 'newtitle')
i managed to change the field values eventually with template_preprocess_views_view_field() but that doesn't work for data export .csv / .xls
created a new views field in hook_views_data and a new plugin extending FieldPluginBase but that that doesn't work with addHandler.
is there a way to add dynamic fields and modify the output or create a new viewsfield and use it with $view->addHandler ?