I am trying to get to grips with Drupal 8s layout and and architecture.

Having worked with Drupal 6 for the last 2 years I have become used to its procedural style, so I am finding the OOP approach takes a little getting used to.

This is what Im trying to achieve.

My Module has a block which displays content
The content of that block is refreshed every 5 seconds
This is done with an Ajax call to the server which overwrites the content of the block with the freshly acquired Ajax HTML

So I have gotten the block to display my content on the page easily enough. My problem is now how do I get to the content to refresh. The logic for building the content is contained in functions in my Block class.

I have tried to set up a route in my .yml file to call these functions again to refresh my content via ajax, but I get fatal errors, and also it does not feel like the right approach to access my block class. I feel I should be routing to the controller.

but then, how do I get at the functions that I have written to build the content for the block in the first place?

Should I have written all my logic in my Controller? and if so, how do I access it from my block?

**UPDATE**

Attempting the solution suggested by Daniel Wehner below I receive the following error:

        Call to undefined method Drupal\livequotes\Controller\LivequotesController::getEntityManager() 
    in <b>C:\Work\excel-8\modules\livequotes\lib\Drupal\livequotes\Controller\LivequotesController.php

I guess this is because I need to extend my controller or to implement the class that defines getEntityManager()

any ideas on how to do this?

**UPDATE 2**

Following on the suggestion in comments from Daniel Wehners answer I have attempted to use dependency injection to give access to EntityManager from my controller. 

This is the code for my controller:

        namespace Drupal\livequotes\Controller;
    
        class LivequotesController{
    	
    	protected $entity;
    	
    	public function __construct(EntityManager $em) {
    		$this->entity = $em;
    	}
    	/**
    	 * Re-render a specific block (yeah if we do something it should be generic).
    	 */
    	public function livequotesShowBlock() 
    	{
    		$block = $this->entity->getStorage('block')->load($block_id);
    		return $this->entity->getViewBuilder('block')->view($block);
    	}
    }

The following error is received when I try and access function livequotesShowBlock() from my ajax call:


> Recoverable fatal error</em>: Argument 1 passed to Drupal\livequotes\Controller\LivequotesController::__construct() must be an instance of Drupal\livequotes\Controller\EntityManager, none given

**UPDATE 3**

Following the link to an example of Dependency injection into a Controller class, [drupal.org/node/2168121][1] provided by Daniel Wehners comment in his answer my Controller now looks like this:

    namespace Drupal\livequotes\Controller;
    use Drupal\Core\Entity\EntityInterface;
    use Drupal\Core\Controller\ControllerBase;
    
    /**
     * Controller routines for livequotes routes.
     */
    
    class LivequotesController extends ControllerBase{
    	
    	protected $entity;
    	
    	public function create(Container $container) 
    	{
    		return new static($container->get('entity'));
    	}
    	
    	public function __construct(EntityInterface $em) {
    		$this->entity = $em;
    	}
    
    	public function livequotesShowBlock() 
    	{
    		$block_id = "livequotes_content";
    		$block = $this->entity->getStorage('block')->load($block_id);
    		return $this->entity->getViewBuilder('block')->view($block);
    	}
    }

Unfortunately though, I am now getting the following error:

> Fatal error: Cannot make static method
> Drupal\Core\Controller\ControllerBase::create() non static in class
> Drupal\livequotes\Controller\LivequotesController in
> C:\Work\excel-8\modules\livequotes\lib\Drupal\livequotes\Controller\LivequotesController.php
> on line 16

**UPDATE 4**

Changing the signature to static

        namespace Drupal\livequotes\Controller;
    use Drupal\Core\Entity\EntityInterface;
    use Drupal\Core\Controller\ControllerBase;
    
    /**
     * Controller routines for livequotes routes.
     */
    
    class LivequotesController extends ControllerBase{
    	
    	protected $entity;
    
    	public static function create(Container $container) {
    		return new static($container->get('entity'));
    	}
    	
    	public function __construct(EntityInterface $em) {
    		$this->entity = $em;
    	}
    	/**
    	 * Re-render a specific block (yeah if we do something it should be generic).
    	 */
    	public function livequotesShowBlock() 
    	{
    		$block_id = "livequotes_content";
    		$block = $this->entity->getStorage('block')->load($block_id);
    		return $this->entity->getViewBuilder('block')->view($block);
    	}
    }

results in the following error:

>  Declaration of
> Drupal\livequotes\Controller\LivequotesController::create() must be
> compatible with
> Drupal\Core\DependencyInjection\ContainerInjectionInterface::create(Symfony\Component\DependencyInjection\ContainerInterface
> $container)

  [1]: http://drupal.org/node/2168121