Embedding a custom form in node.tpl.php does not trigger validation

Question

I'm trying to render a custom form in node.tpl.php.

The form is rendered properly and submit handler works.
However, the validation handler is not triggered properly upon submitting. If I refresh the page, the error message is only then displayed.

Here's the sample module code:

function sample_custom_form() {
  $form['sample_field'] = array(
    '#type' => 'textfield',
    '#title' => t('Enter something'),
  );
  $form['actions'] = array('#type' => 'actions');
  $form['actions']['submit'] = array(
    '#type' => 'submit',
    '#value' => t('Submit'),
  );

  return $form;
}

function sample_custom_form_validate(&$form, &$form_state) {
  if ($form_state['values']['sample_field'] == 'error') {
    form_set_error('sample_field', t('This is a validation error'));
  }
}

function sample_custom_form_submit(&$form, &$form_state) {
  drupal_set_message(t('You entered: @value', array('@value' => $form_state['values']['sample_field'])));
}

In hook_preprocess_node():

$form = drupal_get_form('sample_custom_form');
$variables['custom_form'] = drupal_render($form);

In node.tpl.php:

<?php print $custom_form; ?>

Any ideas what am I doing wrong?
Why isn't the validation handler invoked properly?

Answer 1

$form_state['values']['sample_field'] this value is set after submit, so you validate the old result instead of your actual form.

maybe this workflow helps you