[SOLVED] Need some help with a simple dependency injection

By incursus on 22 Jul 2016 at 17:24 UTC

I'm sure I must be missing the obvious - been staring at this for way too long, and am about to pull my hair out lol.

I am trying to inject a dependency for the database connection into a block class. Here are the relevants:

namespace Drupal\mymodule\Plugin\Block;

use Drupal\Core\Block\BlockBase;
use Drupal\Core\Database\Connection;
use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;

class MyModuleBlock extends BlockBase implements ContainerFactoryPluginInterface {

  protected $connection;

  public function __construct( Connection $connection ) {
    $this->connection = $connection;
  }

  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
    return new static(
      $configuration,
      $plugin_id,
      $plugin_definition,
      $container->get('database')
    );
  }

  ...
}

I have this in my services YML file:

services:
  mymodule.mymodule_block:
    class: Drupal\mymodule\Plugin\Block\MyModuleBlock
    arguments: ['@database']

And I keep getting this error:

 Recoverable fatal error: Argument 1 passed to Drupal\\mymodule\\Plugin\\Block\\MyModuleBlock::__construct() must be an instance of Drupal\\Core\\Database\\Connection, array given ...

I appreciate any guidance! Thanks in advance!

Comments

Never mind, I walked away for

incursus commented 22 July 2016 at 17:39

Never mind, I walked away for a few minutes, came back, and was like WTF? Fixed it .... lol.

Cheers.

For the rest of us - could

Sam Moore

he/him

Sandy Hook, CT

commented 24 July 2016 at 14:38

For the rest of us - could you kindly
- marked your issue "SOLVED" by editing the title, and
- post what you did to fix it?
Future strugglers will thank you.

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Good point :)

incursus commented 24 July 2016 at 23:48

Here is the working code:

namespace Drupal\mymodule\Controller;

use Drupal\Core\Controller\ControllerBase;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Drupal\Core\Database\Connection;

class MyModuleController extends ControllerBase {

  protected $connection;

  public function __construct( Connection $connection) {
    $this->connection = $connection;
  }

  public static function create(ContainerInterface $container) {
    return new static(
      $container->get('database'),
    );
  }

  ...

}

A little problem with your code.

drupalfever commented 29 July 2016 at 23:56

Hello, Scott Burkett! Thanks for sharing this information with the community.

First of all, the code you shared has an extra comma at the end of the following line:
$container->get('database'),

I actually have created a Controller in one of my custom modules and tried your code with no success.

I am pretty frustrated after spending a whole day trying to implement "Database Injection" without success. The documentation on this subject is virtually none existent. People talk about it but there is no practical example.

Would you mind making a small example module that shows how to create and use a "Database Injection"?

By the way, I keep getting

drupalfever commented 30 July 2016 at 00:14

By the way, I keep getting the same error message when using your code:

__construct() "must be an instance of Drupal\Core\Database\Connection, none given

I tried first to create a Controller using this following lines of code I found elsewhere without success:

use Drupal\Core\Database\Connection;

class DatabaseQueryExample {

  protected $connection;

  public function __construct(Connection $connection) {
    $this->connection = $connection;
  }

  public function queryExamples($sql) {
    // db_query()
    $this->connection->query("$sql");
  }
}

What is funny is that I got the same error message!

Did you remember to add the

incursus commented 30 July 2016 at 02:04

Did you remember to add the service tag entry in your mymodule.services.yml file? It should look something like this:

  mymodule.my_controller:
    class: Drupal\mymodule\Controller\MyController
    arguments: ['@database']

Working example

Tsegaye commented 31 July 2018 at 20:45

#report.routing.yml
report.dbtesting:
  path: '/dbtesting'
  defaults:
    _controller: Drupal\report\Controller\dbTest::showContent
  requirements:
    _permission: 'access content'

In my report.services.yml, I have:

services:
      drupal.testcontroller:
        class: Drupal\report\Controller\dbtest
        arguments: ['@database']

In my dbtest.php controller, I have:

<?php

namespace Drupal\report\controller;


use Drupal\Core\Controller\ControllerBase;
use Drupal\Core\Database\Connection;
use Symfony\Component\DependencyInjection\ContainerInterface;

class dbTestController extends ControllerBase {

  /**
   * @var \Drupal\Core\Database\Connection
   */
  private $connection;

  public function __construct(Connection $connection) {
    $this->connection = $connection;
  }

  public static function create(ContainerInterface $container) {
    return new static(
      $container->get('database')
    );
  }

  public function showContent() {
    //db_select is deprecated
    $select = $this->connection->select('node', 'n');
    $select->fields('n');
    $select->condition('type', "article", "=");
    $entries = $select->execute()->fetchAll(\PDO::FETCH_ASSOC);
    $article_count = count($entries);
    return [
      '#markup' => t('There are @articles articles on the current site.', ['@articles' => $article_count])
    ];
  }
}

create() method is unnecessary

imclean commented 15 January 2020 at 23:11

You don't need the create() method as you've listed @database in your *.services.yml file. This passes the service directly to the constructor. See: Services and Dependency Injection

You would then specify the service and method in your *.routing.yml instead of the controller. See: https://www.drupal.org/docs/8/api/routing-system/structure-of-routes