Drupal 8/9 Add or Remove the number of fields dynamically using Ajax Form API

lakshmi, Credit to volkotech-solutions Mar 25

In this example, we are using a field to get a list of taxonomy term tags, with the number of tags being dynamic.

TagsForm.php

<?php
//Add tags field.
public function buildForm(array $form, FormStateInterface $form_state, $username = NULL) {
    $form['tags'] = [
      '#type' => 'details',
      '#title' => "Tags",
      '#open' => TRUE,
      '#description' => "The description of the field.",
    ];
    $form['tags']['addtag'] = [
      '#type' => 'submit',
      '#value' => t('Add one more'),
      '#submit' => ['::addOneTag'],
      '#weight' => 100,
      '#ajax' => [
        'callback' => '::updateTagCallback',
        'wrapper' => 'tagfields-wrapper',
        'method' => 'replace',
      ],
    ];
    $form['tags']['remtag'] = [
      '#type' => 'submit',
      '#value' => t('Remove the last'),
      '#submit' => ['::remOneTag'],
      '#weight' => 100,
      '#ajax' => [
        'callback' => '::updateTagCallback',
        'wrapper' => 'tagfields-wrapper',
        'method' => 'replace',
      ],
    ];
    $form['tags']['tag_values'] = [
      '#type' => 'container',
      '#tree' => TRUE,
      '#prefix' => '<div id="tagfields-wrapper">',
      '#suffix' => '</div>',
    ];
    $number_of_tags = $form_state->get('number_of_tags');
    if (empty($number_of_tags)) {
      $number_of_tags = 1;
      $form_state->set('number_of_tags', $number_of_tags);
    }
    for ($i = 0; $i < $number_of_tags; $i++) {
      $form['tags']['tag_values'][$i] = [
        '#type' => 'entity_autocomplete',
        '#target_type' => 'taxonomy_term',
      ];
    }
    return $form;
}

//Add Callback methods.
/**
  * Add or Increment number of tags.
  */
public function addOneTag(array &$form, FormStateInterface $form_state) {
    $number_of_tags = $form_state->get('number_of_tags');
    $form_state->set('number_of_tags', $number_of_tags + 1);
    $form_state->setRebuild(TRUE);
}
/**
  * Remove or Decrement number of tags.
  */
public function remOneTag(array &$form, FormStateInterface $form_state) {
    $number_of_tags = $form_state->get('number_of_tags');
    $form_state->set('number_of_tags', $number_of_tags - 1);
    $form_state->setRebuild(TRUE);
}
/**
  * Return the tag list (Form).
  */
public function updateTagCallback(array &$form, FormStateInterface $form_state) {
    return $form['tags']['tag_values'];
}

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Muna Vijaya Lakshmi

Drupal developer at VolkoTech Solutions

Drupal backend developer having 2+ years of experience in Drupal site development(8 & 9) with Developing Custom modules and Overriding theme concepts.

VolkoTech Solutions

Drupal development company in india

Drupal web development & Consulting company in India.

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Drupal 8/9 Add or Remove the number of fields dynamically using Ajax Form API

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Muna Vijaya Lakshmi

VolkoTech Solutions

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