/**
  * Ajoute un champ au formulaire
  *
  * @param string $name    Le nom du champ
  * @param \form\Field $field l'objet champ
  * @param int $iteration iteration du champ / si null, champ unique
  *
  * @return $this->fields
  */
 protected function addField($name, \form\Field $field, $iteration = null)
 {
     $real_field_name = $this->get_name() . "[" . $name . "]";
     if (!is_null($iteration)) {
         $real_field_name .= "[" . $iteration . "]";
     }
     $field->add_param('name', $real_field_name);
     if (isset($this->post[$this->get_name()][$name])) {
         if (!is_null($iteration)) {
             $field->add_param('value', $this->post[$this->get_name()][$name][$iteration]);
         } else {
             $field->add_param('value', $this->post[$this->get_name()][$name]);
         }
     }
     if (!is_null($iteration)) {
         $this->fields[$name][$iteration] = $field;
     } else {
         $this->fields[$name] = $field;
     }
     return $this->fields;
 }