How do I check by default a checkbox from a checkboxes control after an AJAX call

Question

I have the next form which behavior is:

• When you select an option from select control, different checkbox are load on checkboxes control.

• When you check/uncheck checkbox a message is showed on the botton with info about select value and checkbox clicked.

Everything works fine, but is impossible check by default a checkbox from checkboxes control after ajax function.

Any idea?

namespace Drupal\drupal_miseries\Form;

use Drupal\Core\Form\FormBase;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Render\Element\Checkboxes;

class CheckboxesAjax extends FormBase {

    protected $values = [
        'select' => [
            '1' => 'Value1',
            '2' => 'Value2',
        ],
        // Options when select 1 is selected
        'checkboxes_v1' => [
            '1' => 'checkbox1',
            '2' => 'checkbox2',
        ],
        // Options when select 2 is selected
        'checkboxes_v2' => [
            '3' => 'checkbox3',
            '4' => 'checkbox4',
        ],
        // Default values for checkboxes
        'checkboxes_df' => [
            // Default value when checkboxes_v1 is showed
            '1' => ['1' => '1', '2' => '0'],
            // Default value when checkboxes_v2 is showed
            '2' => ['3' => '0', '4' => '1'],
        ],
    ];

    public function getFormId() {
        return 'drupal_miseries_checkboxesajax';
    }

    public function selectAjaxCallback(array &$form, FormStateInterface $form_state) {
      return $form['container'];
    }

    public function checkboxesAjaxCallback(array &$form, FormStateInterface $form_state) {
      $checkbox = $form_state->getTriggeringElement();
      $select = $form_state->getValue('select');

      $form['status']['mensaje'] = [
          '#markup' => '
Select: '.$select.' '.$checkbox['#title'].' clicked.'.'
',
      ];

      return $form['status'];
    }

    public function buildForm(array $form, FormStateInterface $form_state) {
      $form['select'] = [
        '#type' => 'select',
        '#title' => $this->t('Select form control'),
        '#options' => $this->values['select'],
        '#default_value' => key($this->values['select']),
        '#ajax' => [
            'callback' => [$this, 'selectAjaxCallback'],
            'wrapper' => 'checkboxes_wrapper',
        ],
      ];

      $form['container'] = [
        '#type' => 'container',
        '#attributes' => ['id' => 'checkboxes_wrapper'],
      ];

      $form['container']['checkboxes'] = [
        '#type' => 'checkboxes',
        '#title' => $this->t('Checkboxes form control from select @select',
          [ '@select' => empty($form_state->getValues()) ? 
              $this->values['select'][key($this->values['select'])] : $form_state->getValue('select') ]),
        '#options' => empty($form_state->getValues()) ?
          $this->values['checkboxes_v1'] :
          $this->values['checkboxes_v'.$form_state->getValue('select')],
        '#default_value' => empty($form_state->getValues()) ?
          $this->values['checkboxes_df']['1'] :
          $this->values['checkboxes_df'][$form_state->getValue('select')],
        '#ajax' => [
            'callback' => [$this, 'checkboxesAjaxCallback'],
            'wrapper' => 'status',
        ],
      ];

      $form['status'] = [
        '#type' => 'container',
        '#attributes' => ['id' => 'status'],
      ];

      return $form;
    }

    public function submitForm(array &$form, FormStateInterface $form_state) {

    }
}

Answer 1

Thanks @IvanJaros, i have read it and i think i'm doing everything fine but i can't understand why is not working.

I have modify selectAjaxCallback to solve this problem:

public function selectAjaxCallback(array &$form, FormStateInterface $form_state) {
      $select = $form_state->getValue('select');

      foreach ($this->values['checkboxes_df'][$select] as $key => $value) {
        $form['container']['checkboxes'][$key]['#checked'] = $value;
      }
      return $form['container'];
    }

This code works, but i'm not sure if it's the right way to solve this problem.

Thanks.