Form validation handler for book_admin_edit().

Checks that the book has not been changed while using the form.

See also

book_admin_edit_submit()

File

drupal-7.x/modules/book/book.admin.inc, line 102

Administration page callbacks for the Book module.

Code

function book_admin_edit_validate($form, &$form_state) {
  if ($form_state['values']['tree_hash'] != $form_state['values']['tree_current_hash']) {
    form_set_error('', t('This book has been modified by another user, the changes could not be saved.'));
  }
}