I try to theme a custom form in my block.

Here my code :

> 
> boutique.module
> 
> 
> 

```
/**
 * Implements hook_theme().
 */
function boutique_theme() {

  return array(    
        'ajout_panier_form'=> array(
            'render element' => 'form',
            'variables'=> array(
                'form'=> NULL,
            )
  )
  );
}

```

> 
> AjoutPanierForm.php
> 
> 
> 

```
/**
 * Class AjoutBlockForm.
 *
 * @package Drupal\boutique\Form
 */
class AjoutPanierForm extends FormBase {

  /**
   * {@inheritdoc}
   */
  public function getFormId() {
    return 'ajout_panier_form';
  }

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

        $form['#attributes']['oninput']='showPoids.value = poids.value';

        $form['poids'] = array(
            '#type' => 'range',
            '#title' => $this->t('Poids en gramme'),
            '#min' => 500,
            '#max' => 20000,
            '#default_value' => 500,
            '#step' => 100,
            '#attributes'=>array('id'=>array('poids')),
            '#description' => $this->t(""),
            '#required' => TRUE,
        );

        $form['showPoids']=array(
            '#type'=>'markup',
            '#markup'=>'<output id="showPoids" for="poids">500</output>'

        );

      $form['ajouter'] = array(
          '#type' => 'submit',
          '#value' => $this->t('Ajouter'),

      );

    return $form;
  }

  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) {
drupal_set_message('ok');

  }

```

> 
> AjoutPanierBlock.php
> 
> 
> 

```
/**
 * Provides a 'AjoutPanierBlock' block.
 *
 * @Block(
 *  id = "ajout_panier_block",
 *  admin_label = @Translation("Block Ajout panier"),
 * )
 */
class AjoutPanierBlock extends BlockBase {

  /**
   * {@inheritdoc}
   */
  public function build() {

    $form = \Drupal::formBuilder()->getForm('Drupal\boutique\Form\AjoutPanierForm');

    $build = [
        '#theme' => 'ajout_panier_form',
        '#form' => $form,
  ];
    return $build;

  }

}

```

And my template :

> 
> ajout-panier-form.html.twig
> 
> 
> 

```
<form{{ attributes }}>  
    {{ form.poids }} {{ form.showPoids }}
    {{ form.form_build_id }} {# required #}
    {{ form.form_id }} {# required #}
    {{ form.ajouter }}
    {{ children }}
</form>

```

My block call my template and my form is display.
But my submit doesn't call my method in my form controller where i put a

```
drupal_set_message('ok');

```

How add the actions form into template ? 
i have put `{{ children }}` but he doesn't work like the balise `{{ form }}` alone.