Drupal Seed Data

Seed Data
You use seeding to provide initial values for lookup lists,
for demo purposes, proof of concepts and of course for development.

To modules\custom\my_module\src we add a directory called SeedData. We add a file
called SeedDataGenerator.php to modules\custom\offer\src\SeedData.
The class will for now just create a dummy user.

<?php

namespace Drupal\my_module\SeedData;

use Drupal\user\Entity\User;
use Drush\Drush;

/**
 * SeedDataGenerator.
 *
 * @package Drupal\my_module
 */
class SeedDataGenerator {

  /**
   * Function to create a seed data.
   *
   * @param string $entity
   *   The type of entity that needs to be created.
   *
   * @return null|int
   *   The number of entities created.
   */
  public function generate(string $entity){
    $count = 0;
    switch ($entity) {
      case 'user':
        $count = $this->seedUser();
        break;
    }
    return $count;
  }

  /**
   * @return int
   *   The number of users created.
   * @throws \Drupal\Core\Entity\EntityStorageException
   */
  private function seedUser() {
    $count = 0;

    $user = User::create();
    $user->setUsername('testUser');
    $user->setPassword('P@ssw0rd');
    $user->activate();
    $user->enforceIsNew();
    Drush::output()->writeln('<comment>Creating user test</comment>' );
    if ($user->save()) {
      $count++;
    }
    return $count;
  }
}

Proceed with adding a drush command that will trigger the class:
Add custom/my_module/src/Commands/SeedGeneratorCommand.php and configure
further. The final file looks like this:

<?php

namespace Drupal\my_module\Commands;

use Drupal\my_module\SeedData\SeedDataGenerator;
use Drush\Commands\DrushCommands;
use Drush\Drush;

/**
 * Class SeedGeneratorCommand.
 *
 * @package Drupal\my_module\Commands
 */
class SeedGeneratorCommand extends DrushCommands {

  /**
   * Runs the mymoduleCreateSeeds command.
   *
   * @command mymodule-create-seeds
   * @aliases mymodulecs
   * @usage drush mymodule-create-seeds
   * Display 'Seed data created'
   */
  public function mymoduleCreateSeeds():void {
    $seed = new SeedDataGenerator();
    $count = $seed->generate('user');
    Drush::output()->writeln('<info>'. $count . ' user(s) created</info>' );
  }

}

One more thing. Add a file custom/my_module/my_module.services.yml and add:

services:
  offer.commands:
    class: Drupal\offer\Commands\SeedGeneratorCommand
    tags:
      - { name: drush.command }

That’s it! Clear cache and see if our system has registered our command

$drush offer-create-seeds

References:

• Learning drupal 9 as a framework