How to render a form in custom template?

Question

I'm looking to add a form inside a custom template. The form, if I open the path registered inside the file cmodule.routing.yml, works but if i try to use it inside a custom template it doesn't work: with a dump(form) or dump(form.anyfield) i get NULL.

cmodule.routing.yml:

cmodule.manageform:
  path: '/cmodule/manageform'
  defaults:
    _title: 'Documents'
    _form: '\Drupal\cmodule\Forms\RequestForm'
  requirements:
    _permission: 'access content'
cmodule.manage:
  path: '/cmodule/manage'
  defaults:
    _controller: '\Drupal\cmodule\Controller\CmoduleController::manageAction'
    _title: 'Custom Documents'
  requirements:
    _permission: 'access content'

RequestForm.php:

/**
 * {@inheritdoc}
 *
 */
public function buildForm(array $form, FormStateInterface $form_state) {

    $form['type'] = array(
        '#type' => 'radios',
        '#options' => array(
            '0' =>t('DOC'),
            '1' =>t('PDF')
        ),
    );
    $form['pid'] = array(
        '#type' => 'textfield',
        '#title' => t('ID:'),
        '#required' => FALSE
    );
    $form['submit'] = array(
        '#type' => 'submit',
        '#value' => $this->t('Submit'),
        '#attributes'=> ['class'=>['glyphicon', 'glyphicon-search']],
    );


    return $form;
}

cmodule.module:

/**
 * Implements hook_theme().
 */
function cmodule_theme(){

    $templates = array(
        'manage_cmodule_page' => array(
            'variables' =>
                [
                    'id' => NULL,
                    'form' => NULL
                ],
            'template' =>'manage_cmodule',
            'render element' => 'form'
        )
    );

    return $templates;
}

the controller contains:

public function manageAction() {

        $id = 1;

        $form = \Drupal::formBuilder()->getForm('Drupal\cmodule\Forms\RequestForm');

        $form['type']['#title_display'] = 'invisible';

        return [ '#theme' => 'manage_cmodule_page',
            '#form' => $form,
            '#id' => $id,
        ];
    }

and then the template/view (contains):

<div>
 {{ form.form_token }}
{{ form.form_build_id }}
{{ form.form_id }} 
{{form.type}}
{{form.submit}}
</div>
etc..

But as I said above the template doesn't show the form, but show (if i print it) the #id value passed through the controller. Do you have any suggestions?!

---

UPDATE #1 I tried also to follow the suggestion of Beebee, and then this and this so the code is:

controller:

controller contains:

public function manageAction() {

        $form = \Drupal::formBuilder()->getForm('Drupal\cmodule\Forms\RequestForm');

        $render['#form'] = $form;
        $render['theme'] = 'manage_cmodule_page';
        return $render;;
    }

and the implementation of hook_theme in .module file is:

return [
    'manage_cmodule_page' => [
        'template' =>'manage_cmodule',
        'render element' => 'form',
    ]
];

The result is an empty page with an error inside the apache log:

[php7:error] [pid 12660:tid 1592] [client ::1:59521] PHP Fatal error: Out of memory (allocated 270532608) (tried to allocate 266354688 bytes) in C:\drupal\vendor\twig\twig\lib\Twig\Extension\Debug.php on line 60, referer: http://localhost/drupal/

if I remove the following row from the controller

$render['theme'] = 'manage_atps_page';

the page loads, but it is empty (without any form).

UPDATE #2

I fixed my issue following also the idea of Alex Kuzava. Thus I used the code of UPDATE 1, with the new directory of the form, and then I added these 3 lines inside the part of my template (otherwise the submit button doesn't work).

{{ form.form.form_build_id }} 
{{ form.form.form_id }}
{{ form.form.form_token }}

Answer 1

'render element' => 'form'

Your render element is form which means all provided variables will be passed there.

In your twig template you can render your form like here

<div>{{ form.form }}</div>

---

UPDATE #1

Wow man, you have wrong namespace Drupal\cmodule\Forms\RequestForm

Should be Drupal\cmodule\Form\RequestForm

Please rename Forms to Form (the same for directory) and clear cache. It should help you.

Answer 2

See: https://api.drupal.org/api/drupal/core!lib!Drupal!Core!Render!theme.api.php/function/hook_theme/8.2.x

Each information array must contain either a 'variables' element (for using a #theme element) or a 'render element' element (for render elements), but not both.

Your manage_cmodule_page expects both variables and render element which is not allowed. Removing variables array from your hook_theme should make this work, provided the rest of the code is functional.