How to change views field value using a hook

Question

I want to change drupal 8 views field value before displaying. I am using below hook_views_pre_render

function MYMODULE_views_pre_render(ViewExecutable $view) {
  if ($view->id() == "demo1" && $view->current_display == 'page_demo1') {
     foreach($view->result as $value){
      $value->_entity->set('created', $value->_entity->get('created')->value . '-' .($value->_entity->get('changed')->value - $value->_entity->get('created')->value));      
     }
  }
}

I want to time difference between created and changed date time.

but its not working...

Answer 1

You can convert them to int and work with them as integers. For example if you want to set created to changed - created. Here is a working example:

use Drupal\views\ViewExecutable;

function MYMODULE_views_pre_render(ViewExecutable $view){
  if ($view->id() == "views_id" && $view->current_display == 'view_display') {
    foreach ($view->result as $value) {
      $created = (int) $value->_entity->get('created')->value;
      $changed = (int) $value->_entity->get('changed')->value;
      //- If you want for example to set created time with changed - 
      created.
      $value->_entity->set('created', $changed - $created);
    }
  }
}