I Have a Drupal 7 site with a node_presave function which works to enter a start date (date field) and number of days field (integer) which then populates the date field with the correct number of dates. ie Start date : 2018-02-05 Number of days : 3 Output in date field: 2018-02-05 2018-02-06 2018-02-07

Here is the code:

function node_presave($  node) {   if (in_array($  node->type, array('boka_rum'))) {     $  date_field = $  node->field_datum['und'][0];     unset($  node->field_datum['und']);     $  days = intval($  node->field_antal_dagar['und'][0]['value']);     for ($  i = 0; $  i < $  days; $  i++) {       $  node->field_datum['und'][] = $  date_field;       $  date_field['value'] = $  date_field['value2'] = date('Y-m-d 00:00:00',strtotime($  date_field['value'] . "+1 days"));     }   }  } 

I am trying to upgrade this to a Drupal 8 site but am missing something somewhere. Can anyone help with the correct syntax?

Drupal 8 code:

function entity_presave(Drupal\Core\Entity\EntityInterface $  entity) {   if (in_array($  node->type, array('boka_rum'))) {    $  entity->field_datum = $  date_field     unset($  entity->field_datum);    $  entity->field_antal_dagar = $  dagar     $  days = intval($  dagar);     for ($  i = 0; $  i < $  days; $  i++) {       $  entity->field_datum = $  date_field;       $  date_field['value'] = $  date_field['value2'] = date('Y-m-d 00:00:00',strtotime($  date_field['value'] . "+1 days"));     }   } 

}

Thanks