How can I uncheck a required checkbox on the edit page for a given content type?

Question

I have a "required" checkbox (single on-off boolean field) which users must check to agree to the rules of the site when they post a node of a certain content type. When users edit nodes of this content type, I would like to reset the checkbox to force them to check it again.

How can I do this in Drupal 7?

Answer 1

Implement hook_form_FORM_ID_alter() such that it clears the #default_value property of the widget:

function mymodule_form_node_form_alter(&$form, &$form_state, $form_id) {
  $node_type = 'example_type'; // TODO: change to the desired node type
  $field = 'field_example';    // TODO: change to the name of the field

  $node = $form['#node'];
  if ($node->type == $node_type) {
    $language = $form[$field]['#language'];
    $form[$field][$language]['#default_value'] = 0;
  }
}

Answer 2

I can't comment on the other answer, but you can set a default value of an empty array (not 0 or FALSE to avoid a PHP warning):

$form[$field][$language]['#default_value'] = array();

See https://www.drupal.org/project/drupal/issues/3009881#comment-13407511

I would also add a condition to only set this default value on a node/add form, because #default_value will override any existing checked box and blank it out again on an edit form. I used:

if (!isset($node->nid) || isset($node->is_new)) {
  $form['field_mycheckbox'][LANGUAGE_NONE]['#default_value'] = array();
}