9.14.1. Extending custom Drupal Views filter handler

In the previous article we had a look how to integrate Views modules with custom database for Did this help? module:

https://www.drupal.org/project/did_this_help

In this articles we will override Views filter for  Choice (yes/no) field:

Now it's usual text field created by "string" handler, which allows to add search key. But we have only two options Yes/No, so it would be better to have dropbox instead of textfield. Let's create a file /did_this_help/src/Plugin/views/filter/DidThisHelp.php:

<?php

namespace Drupal\did_this_help\Plugin\views\filter;

use Drupal\views\Plugin\views\filter\InOperator;

/**
 * Filters by given list of yes/no options.
 *
 * @ingroup views_filter_handlers
 *
 * @ViewsFilter("did_this_help")
 */
class DidThisHelp extends InOperator {

}

We will inherit DidThisHelp class from parent InOperator class, which provides filter with select dropbox, radio buttons or checkboxes depends on Views UI settings. 

In method getValueOptions() we will add list of available options:

  /**
   * {@inheritdoc}
   */
  public function getValueOptions() {
    if (isset($this->valueOptions)) {
      return $this->valueOptions;
    }

    $this->valueOptions = [
      'yes' => $this->t('Yes'),
      'no' => $this->t('No'),
    ];

    return $this->valueOptions;
  }

Property valueOptions has been defined in parent class InOperator, so we need to define only array of options.

In results we got that filter:

If we enabled exposed filter, then we see this dropbox:

You can override any Filter class from this list of classes provided by Views and other modules: