I have a custom module that creates a field type. It is a plain text field abd I’ve added it to a content type using the Drupal UI. The cardinality of this field is "Unlimited".

This is how I create the field in code:

 class MyItem extends FieldItemBase {    /**    * {@inheritdoc}    */   public static function schema(FieldStorageDefinitionInterface $field_definition) {     return [       'columns' => [         'value' => [           'type' => 'text',           'size' => 'tiny',           'not null' => FALSE,         ],         'safevalue' => [           'type' => 'text',           'size' => 'tiny',           'not null' => FALSE,         ],       ],     ];   }    /**    * {@inheritdoc}    */   public static function propertyDefinitions(FieldStorageDefinitionInterface $field_definition) {     $properties['value'] = DataDefinition::create('string')       ->setLabel(t('Value'));     $properties['savevalue'] = DataDefinition::create('string')       ->setLabel(t('Safe value'))       ->setComputed(TRUE);     return $properties;   }  } 

As you can see, there are two columns: value is supposed to store raw user input. safevalue is supposed to store a sanitized version of the data.

For testing this. I am just doing this inside hook_node_presave():

 function mymodule_node_presave(DrupalCoreEntityEntityInterface $entity) {   switch ($entity->getBundle()) {     case 'mybundle':       $entity->field_myfield = ['one', 'two', 'three'];       $entity->field_myfield->safevalue =  ['one', 'two', 'three'];       break;   } } 

If the field has a cardinality 1 (i.e. the values inserted are scalars), this works fine.

However, if I insert arrays, when I examine the database, and look at the table node__field_myfield, I see that the columns field_myfield_value and field_myfield_safevalue both exist with identical configurations.

If I create a node using the UI, I observe this:

• field_myfield_value column contains three rows with the strings ‘one’, ‘two’ and ‘three’. That’s correct.
• field_myfield_safevalue have the string ‘Array’ in its first row, and NULL in the two others. That’s wrong.

I guess that what makes things go wrong is that this is a multivalue field and that I need to use some other action to get the values correctly inserted.

How can I get a multivalue field correctly inserted in the safevalue column?