How do I render content generated by a controller in a custom block?

Question

To render a form in a block, I can use the following code.

class LoremIpsumBlock extends BlockBase {

  public function build() {
    // Return the form @ Form/LoremIpsumBlockForm.php.
    return \Drupal::formBuilder()->getForm('Drupal\loremipsum\Form\LoremIpsumBlockForm');
  }

How can I render in a block the output of a controller? Is it possible, or do I have to duplicate the controller class code in the block class?

The example in the documentation is too simple and it shows how to render a literal string.

class HelloBlock extends BlockBase {

  public function build() {
    return array(
      '#markup' => $this->t('Hello, World!'),
    );
  }    
}

Answer 1

you can call the controller class inside the custom block,

check this below example,

Controller:

   <?php

    namespace Drupal\custom_example\Controller;


    class ExampleController {

         public function example(){

           return array(
             '#title' => 'Example',
             '#markup' => 'This is a custom module', 

            );
         }
    }

custom Block: Here, Use the ExampleController like this,

 use Drupal\custom_example\Controller\ExampleController;

ExampleController should be the class name of the Controller

<?php

namespace Drupal\custom_example\Plugin\Block;


use Drupal\Core\Block\BlockBase;
use Drupal\custom_example\Controller\ExampleController;

class CustomBlock extends BlockBase {

  public function build() {

     $controller_variable = new ExampleController;
     $rendering_in_block = $controller_variable->example();
     return $rendering_in_block;

  }

}

Create the new instance using the class name and call the function in the block

Answer 2

@4k4 is correct in their answer that it is preferable to refactor the shared code into a separate class (probably a service).

However, if that is not an option (because you are building on core or contributed code that you cannot change) it is still possible to re-use the output of a controller that uses dependency injection (DI). To do so, inject the class_resolver service into your block and use it to get a controller object. Your block code would look something like this:

<?php

namespace Drupal\my_module\Plugin\Block;

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

/**
 * Provides a custom block containing the output of a controller.
 *
 * @Block(
 *  id = "controller_block",
 *  admin_label = @Translation("Controller block"),
 * )
 */
class ControllerBlock extends BlockBase implements ContainerFactoryPluginInterface {

  /**
   * Class Resolver service.
   *
   * @var \Drupal\Core\DependencyInjection\ClassResolverInterface
   */
  protected $classResolver;

  /**
   * Constructs a new ControllerBlock object.
   *
   * @param array $configuration
   *   A configuration array containing information about the plugin instance.
   * @param string $plugin_id
   *   The plugin_id for the plugin instance.
   * @param string $plugin_definition
   *   The plugin implementation definition.
   * @param \Drupal\Core\DependencyInjection\ClassResolverInterface $class_resolver
   *   The class resolver service.
   */
  public function __construct(
    array $configuration,
    $plugin_id,
    $plugin_definition,
    ClassResolverInterface $class_resolver
  ) {
    parent::__construct($configuration, $plugin_id, $plugin_definition);
    $this->classResolver = $class_resolver;
  }

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
    return new static(
      $configuration,
      $plugin_id,
      $plugin_definition,
      $container->get('class_resolver')
    );
  }

  /**
   * {@inheritdoc}
   */
  public function build() {
    // Assuming that \Drupal\my_module\Controller\MyController::build is a
    // public function that returns the controller output.
    $controller = $this->classResolver->getInstanceFromDefinition('\Drupal\my_module\Controller\MyController');
    return $controller->build();
  }

}

Answer 3

A controller depends on a request and route match. In simple cases you can treat the controller like a normal class, but more complex controllers with DI and route arguments will fail. You should refactor the code so that the shared content of the controller and block is built in a different place both have access to, like this is the case in your block example, where this is a form.

Answer 4

Use namespace for your controller like:

"use Drupal\your_custom_module\Controller\your_class_name;"

then you can call the function of "your_class_name", where you have generated all the tables/html, inside you build() of Class "HelloBlock" .

Answer 5

Either the part of the code used by the controller and the block is implemented by a service, or the block code instances the controller using the controller_resolver service.

namespace Drupal\mymodule\Plugin\Block;

use Drupal\Core\Block\BlockBase;
use Drupal\Core\Controller\ControllerResolverInterface;
use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;

/**
 * Provides a custom block that shows a controller's output.
 *
 * @Block(
 *  id = "mymodule_block",
 *  admin_label = @Translation("Mymodule block"),
 * )
 */
class MymoduleBlock extends BlockBase implements ContainerFactoryPluginInterface {

  /**
   * The controller resolver service.
   *
   * @var \Drupal\Core\Controller\ControllerResolverInterface
   */
  protected $controllerResolver;

  /**
   * Constructs a new \Drupal\mymodule\Plugin\Block\MymoduleBlock object.
   *
   * @param array $configuration
   *   A configuration array containing information about the plugin instance.
   * @param string $plugin_id
   *   The plugin_id for the plugin instance.
   * @param string $plugin_definition
   *   The plugin implementation definition.
   * @param \Drupal\Core\Controller\ControllerResolverInterface $controller_resolver
   *   The controller resolver service.
   */
  public function __construct(array $configuration, $plugin_id, $plugin_definition, ControllerResolverInterface $controller_resolver) {
    parent::__construct($configuration, $plugin_id, $plugin_definition);
    $this->controllerResolver = $controller_resolver;
  }

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
    return new static(
      $configuration,
      $plugin_id,
      $plugin_definition,
      $container->get('controller_resolver')
    );
  }

  /**
   * {@inheritdoc}
   */
  public function build() {
    // $controller is a string "$class_or_service:$method" or "$class_or_service::$method".
    $callable = $this->controllerResolver->getControllerFromDefinition($controller);
    // $callable is an array [$object, $method].
  }

}