How do I create multiple blocks?

Question

I would like to create multiple blocks using the data rendered from the variable table in Drupal 8. I was able to achieve it in Drupal 7, but I can't find a way to do the same in Drupal 8.

The code I use for Drupal 7 is the following.

/**
 * Create a block that will display the calendar feed
 * Implements hook_block_info
 */
function my_module_block_info() {
  $blocks = array();
  $block_urls = variable_get('my_module_content');
  $block_regions = variable_get('my_module_content_block_region');
  $number_of_blocks = count($block_urls);
  if ( $number_of_blocks > 0 ) {
    foreach ( $block_urls as $key => $block_url ) {
      $blocks['eventblock-' . $key] = array(
        'info' => t('my_module_widget_block_' . $key), 
        'status' => TRUE,
        'region' => $block_regions[$key],
        'cache' => DRUPAL_NO_CACHE,
      );
    }
  }
  return $blocks;
}

/**
 * Render the my_module block
 * Implements hook_block_view
 */
function my_module_block_view($delta = '') {
  $block = array();
  $block_urls = variable_get('my_module_content' , array());
    foreach ( $block_urls as $key => $block_url ) {
      switch ($delta) {
        case 'eventblock-' . $key:
          $widgetURL= $block_urls[$key];
          $block['content'] = my_module_content_generate($widgetURL); // Some function to generate block content.
          break;
        }
    }

  return $block;
}

Answer 1

In order to create blocks dynamically in Drupal 8, you will have to define a plugin derivative. Plugin Derivatives.

This way you can create multiple instances of the same block. Hope this helps.

Block Derivatives Example

Remember to respect the folder structure when creating your derivative and block class.

Derivative

<?php

namespace Drupal\YOUR_MODULE_NAME\Plugin\Derivative;

use Drupal\Component\Plugin\Derivative\DeriverBase;

class YOUR_DERIVATIVE_NAME extends DeriverBase {

/**
 * {@inheritdoc}
 */
public function getDerivativeDefinitions($base_plugin_definition) {
// @todo might as well include your configuration here and assign a value.
  $block_urls = ['1', '2', '3'];

  foreach ($block_urls as $block_url) {
    $this->derivatives[$block_url] = $base_plugin_definition;
    $this->derivatives[$block_url]['admin_label'] = 'Sample Label ' . $block_url;
  }

  return $this->derivatives;
  }

}

Block

<?php

namespace Drupal\YOUR_MODULE_NAME\Plugin\Block;

use Drupal\Core\Access\AccessResult;
use Drupal\Core\Block\BlockBase;
use Drupal\Core\Session\AccountInterface;


/**
 * Provides a block.
 *
 * @Block(
 *   id = "YOUR_BLOCK_ID",
 *   admin_label = @Translation("YOUR_BLOCK_ID"),
 *   deriver = "Drupal\YOUR_MODULE_NAME\Plugin\Derivative\YOUR_DERIVATIVE_NAME"
 * )
 */

class YOUR_BLOCK_NAME extends BlockBase {

  /**
   * {@inheritdoc}
   */
  public function build() {
    $id = $this->getDerivativeId();

    $build = [
      '#markup' => $this->t('Your Block Content with ID' . $id),
    ];

    return $build;
  }

  /**
   * {@inheritdoc}
   */
  protected function blockAccess(AccountInterface $account) {
    return AccessResult::allowedIfHasPermission($account, 'access  content');
  }

}

Rename YOUR_MODULE_NAME, YOUR_BLOCK_NAME, YOUR_BLOCK_ID, YOUR_DERIVATIVE_NAME accordingly.