How to specify radio buttons in baseFieldDefinitions?

Question

In the baseFieldDefinitions method of my custom entity, I see I can provide a checkbox list with code like...

$fields['my_field'] = BaseFieldDefinition::create("list_string")
      ->setSetting('allowed_values', $$my_options)
      ->setLabel('My Field')
      ->setRequired(FALSE)
      ->setCardinality(-1)
      ->setDisplayOptions('form', array(
        'type' => 'options_buttons',
        'weight' => 5
      ))
      ->setDisplayConfigurable('form', TRUE)
      ->setDisplayConfigurable('view', TRUE);

But how would I specify radio buttons so the user can make only one selection from the list?

Answer 1

The radios/checkboxes are displayed based on the field's cardinality:

• If the field can store more than one (e.g., unlimited: ->setCardinality(-1), or 2,3,etc. ->setCardinality(2), ->setCardinality(3), etc.), it will be displayed as checkboxes.
• If the field can store only one (i.e. ->setCardinality(1)), it will be displayed as radio buttons.