Entity Reference and integer

Create an entity reference field and an integer field.

In this example will be creating a field that has both an entity reference field and an integer field.

FieldType

The FieldType is the class that will handle the storage of the field. It will be responsible for storing the data in the database and retrieving it. It will also be responsible for validating the data.

<?php

namespace Drupal\MODULE_NAME\Plugin\Field\FieldType;

use Drupal\Core\Field\FieldStorageDefinitionInterface;
use Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem;
use Drupal\Core\TypedData\DataDefinition;

/**
 * @FieldType(
 *   id = "YOUR_FIELD_TYPE_ID",
 *   label = @Translation("THE LABEL THAT WILL BE DISPLAYED"),
 *   description = @Translation("A SIMPLE DESCRIPTION OF THE FIELD"),
 *   category = @Translation("THE CATEGORY WHERE IT WILL BE DISPLAYED"),
 *   default_widget = "YOUR_DEFAULT_WIDGET",
 *   default_formatter = "YOUR_DEFAULT_FORMATTER",
 * )
 */
class FieldTypeName extends EntityReferenceItem {
  public static function propertyDefinitions( FieldStorageDefinitionInterface $field_definition ) {

    $properties              = parent::propertyDefinitions( $field_definition );
    
    $priority_definition     = DataDefinition::create( 'integer' )
                                             ->setLabel( t( 'Priority' ) )
                                             ->setRequired( true ); // If we want the field to be required
    $properties['priority'] = $priority_definition;

    return $properties;
  }

  public static function schema( FieldStorageDefinitionInterface $field_definition ) {
    $schema                         = parent::schema( $field_definition );

    // The schema normally used in Drupal for integer fields
    $schema['columns']['priority'] = array(
      'type'     => 'int',
      'size'     => 'normal',
      'unsigned' => true,
    );

    return $schema;
  }

  /**
   * {@inheritdoc}
   */
  public function isEmpty() {
    if ( ! empty( $this->priority ) ) {
    // If the field is not empty, we return false and the information is saved
      return false;
    }
    return true;
  }

}

FieldWidget

The FieldWidget is the class that will handle the display of the field in the form. It will be responsible for displaying the field in the form and handling the data that is sent from the form.

<?php

namespace Drupal\MODULE_NAME\Plugin\Field\FieldWidget;

use Drupal\Core\Field\FieldItemListInterface;
use Drupal\Core\Field\Plugin\Field\FieldWidget\EntityReferenceAutocompleteWidget;
use Drupal\Core\Form\FormStateInterface;

/**
 * @FieldWidget(
 *   id = "YOUR_DEFAULT_WIDGET",
 *   label = @Translation("THE LABEL THAT WILL BE DISPLAYED"),
 *   description = @Translation("A SIMPLE DESCRIPTION OF THE FIELD"),
 *   field_types = {
 *     "YOUR_FIELD_TYPE_ID"
 *   }
 * )
 */
class FieldWidgetName extends EntityReferenceAutocompleteWidget {
  public function formElement( FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state ) {
    $widget = parent::formElement( $items, $delta, $element, $form, $form_state );

    $widget['priority'] = array(
      '#title'         => $this->t( 'Priority' ),
      '#type'          => 'number',
      '#default_value' => isset( $items[ $delta ] ) ? $items[ $delta ]->priority : 1, // If no value is set, we set it to 1
      '#min'           => 1,
      '#weight'        => 10,
    );

    return $widget;
  }
}

FieldFormatter

The FieldFormatter is the class that will handle the display of the field in the view. It will be responsible for displaying the field in the view.

<?php

namespace Drupal\MODULE_NAME\Plugin\Field\FieldFormatter;

use Drupal\Core\Field\FieldItemListInterface;
use Drupal\Core\Field\Plugin\Field\FieldFormatter\EntityReferenceLabelFormatter;

/**
 * @FieldFormatter(
 *   id = "YOUR_DEFAULT_FORMATTER",
 *   label = @Translation("THE LABEL THAT WILL BE DISPLAYED"),
 *   description = @Translation("A SIMPLE DESCRIPTION OF THE FIELD"),
 *   field_types = {
 *     "YOUR_FIELD_TYPE_ID"
 *   }
 * )
 */
class FieldFormatterName extends EntityReferenceLabelFormatter {

  public function viewElements( FieldItemListInterface $items, $langcode ) {
    $elements = parent::viewElements( $items, $langcode );
    $values   = $items->getValue();

    foreach ( $elements as $delta => $entity ) {
      $elements[ $delta ]['#suffix'] = ' Priority: ' . $values[ $delta ]['priority'];
    }


    if ( \Drupal::routeMatch()->getRouteName() == 'view.MYVIEW' ) { // OPTIONAL
      foreach ( $elements as $delta => $entity ) {
        $elements[ $delta ]['#prefix'] = '<div class="teaser-title">';
        $elements[ $delta ]['#suffix'] = '</div><div class="teaser-priority">priority: ' . $values[ $delta ]['priority'] . '</div>';
      }
    }// OPTIONAL

    // OPTIONAL: Order by [$values[ $delta ]['priority']]
    usort($elements, function($a, $b) {
      return $a['#suffix'] <=> $b['#suffix'];
    });

    return $elements;
  }
}