Creating content blocks programmatically in Drupal 8

Let's picture this: you've created a custom content block type (let's say, Ad block) in your shiny new Drupal 8 installation and you want to automaticaly create a fresh new block of that type each time you create a taxonomy term (Ad group), so that every ad group has a corresponding ad block.

How do I do that? Simple! Follow ~~the white rabbit~~ me:

1. We add the entity_insert hook and catch our taxonomy term insert event:

   <?php
   /**
   * Implements hook_entity_insert().
   */
   function pabc_ads_entity_insert(Drupal\Core\Entity\EntityInterface $entity) {
   // Catching a term that belongs to the ad_group vocabulary.
   if ($entity->getEntityTypeId() == 'taxonomy_term' && $entity->bundle() == 'ad_groups') {
   
   }
   }
   

2. Next we create our block via EntityManager Drupal service:

   <?php
   // Grab a block entity manager from EntityManager service
   $blockEntityManager = \Drupal::service('entity.manager')
   ->getStorage('block_content');
   
   // Tell block entity manager to create a block of type "ad_block"
   $block = $blockEntityManager->create(array(
   'type' => 'ad_block'
   ));
   
   // Every block should have a description, but strangely it's property
   // is not 'description' but 'info'
   // in my case, I want it to be equal to my ad_group's term name.
   $block->info = $entity->name->value;
   
   // This is optional part, my ad_block has a field field_ad_group
   // which is a taxonomy reference to the ad_group taxonomy,
   // that way I link ad_group and ad_block together.
   $block->field_ad_group = $entity;
   
   // In the end, save our new block.
   $block->save();
   

3. So in the end you code snippet should look like this:

   <?php
   /**
    * Implements hook_entity_insert().
    */
   function pabc_ads_entity_insert(Drupal\Core\Entity\EntityInterface $entity) {
   
     // Catching a term that belongs to the ad_group vocabulary.
     if ($entity->getEntityTypeId() == 'taxonomy_term' && $entity->bundle() == 'ad_groups') {
   
   // Grab a block entity manager from EntityManager service
   $blockEntityManager = \Drupal::service('entity.manager')
   ->getStorage('block_content');
   
   // Tell block entity manager to create a block of type "ad_block"
   $block = $blockEntityManager->create(array(
     'type' => 'ad_block'
   ));
   
   // Every block should have a description, but strangely it's property
   // is not 'description' but 'info'
   // in my case, I want it to be equal to my ad_group's term name.
   $block->info = $entity->name->value;
   
   // This is optional part, my ad_block has a field field_ad_group
   // which is a taxonomy reference to the ad_group taxonomy,
   // that way I link ad_group and ad_block together.
   $block->field_ad_group = $entity;
   
   // In the end, save our new block.
   $block->save();
     }
   
   }
   

As you see, creating content blocks in Drupal 8 is pretty similar to creating any other type of entity (node or taxonomy), you just need to figure out a correct service to do that and check what fields should be filled in.