Distill

Distill is a Drupal module that enables other modules to extract and format data from Drupal entities. It provides a simple class structure for defining formatting schemas.

How does Distill Work?

Distill contains 2 classes. 1) A class that defines the structure of a processor and 2) a distillation class that takes an entity, a processor class, and a list of fields that should be returned, executes the processor’s formatter methods, and returns an array of data. If the processor passed into the distillation class doesn't have a processor for a specific field type, then it will default to invoking the hook defined for that field type.

Distill class

Distill is a class that takes an entity type, entity, processor, and language. When asked, it will go through fields, process them with the methods as defined in the passed-in processor (defaulting to the field type hooks if no processor function is available), and add them to an array of field values. It contains a few methods that allow you to ask for fields, and grab field values.

• setField('field_name', 'property_name', array('settings')): Asks the distiller to process a given field, and add it to the array of processed fields with the key as specified in the property_name parameter. This function also takes a settings array, which gets passed into the processor class and allows one to pass context to the processor function.
• setAllFields(): Tells the distiller that all fields should be formatted and returned.
• getFieldValues(): Returns the array of field data that has been extracted from the given entity and processed by the distiller.

DistillProcessor class

The DistillProcessor class contains methods that provide a sensible default for extracting and formatting data from fields. The methods are called based on the field type, or name.

You can create your own processor class that extends DistillProcessor, and easily override processor methods by simply creating methods in the following pattern:

Field Type Processor Methods

Field type processor methods are called based on the type of field that is currently being processed. The pattern for creating these method names is process*Typename*Type(), where *Typename* is equal to the type of field this method should process (such as Text or Entityreference). If your processor class does not have a method for processing a particular type of field, then it will invoke hook_distill_process_*field_type*(). These hooks should be implemented by the module defining the field type, or within the distill.module file.

Field Name Processor Methods

Field name processor methods are called based on the name of the field that's currently being processed. The patter for creating these method names is process*Fieldname*Field(), where *Fieldname* is equal to the name of the field this method should process (such as Fieldimage or Body).

All processor methods take 3 parameters:

• $wrapper: EntityStructureWrapper|EntityValueWrapper of field from which values are being extracted.
• $index: Integer representing the delta of the field being processed.
• $settings: Variable for passing in settings and context that will affect how the field value should be processed.

Example

Here's a quick example implementation of this module within a route controller:

namespace Drupal\my_module\Controller;
use Drupal\Core\Controller\ControllerBase;
use Symfony\Component\HttpFoundation\JsonResponse;

// Load Distill classes.
use Drupal\distill\Distill;
use Drupal\distill\DistillProcessor;

/**
 * Controller routines for my_module routes.
 */
class DistillExampleController extends ControllerBase {
  /**
   * Returns a blob of yummy json.
   */
  public function exampleDataExtrationEndpoint() {
    $entity = \Drupal::entityManager()->getStorage('node')->load(1);

    // Create instance of processor.
    $processor = new DistillProcessor();

    // Create instance of Distill.
    $distiller = new Distill($entity, $processor);

    // Specify which fields should be returned.
    $distiller->setField('nid', '_id');
    $distiller->setField('title');
    $distiller->setField('body', 'post');

    // We pass in an image style.
    $distiller->setField('field_image', 'image', array('image_style' => 'thumbnail'));

    // This is an entity reference field. We pass a settings array
    // that has an 'include_fields' key. This key contains an array of fields
    // from the referenced entity that should be returned.
    $distiller->setField('field_author', 'user', array(
      'include_fields' => array(
        'name',
        'mail'
      )
    ));

    // Output the returned array as JSON.
    return new JsonResponse($distiller->getFieldValues());
  }
}

And here's an example of an entity that's been processed and formatted as JSON:

{
  title: "Hello World!",
  post: "<p>This is a post body.</p> ",
  image: "http://d7.local/sites/default/files/styles/thumbnail/field/image/whoa.jpg",
  user: {
    name: "admin",
    mail: "[email protected]"
  }
}

What's Next?

Distill is still under development. Here are some things that are likely to surface soon:

• distill_extra module that contains lots of field-type default formatters.
• Drupal 8 version of Distill.
• RestFull/Distill implementation.
• Better documentation.
• Panels pane that allows developers to easily create and theme panes of content.