Drupal 8 & 9: How create a simple custom module for breadcrumbs: Example #1

name: EasyDrupal Breadcrumbs
type: module
description: Setting breadcrumbs for custom content types.
core: 8.x
package: Custom

<?php
/**
* @file
* Contains easydrupal_breadcrumb.module.
*/
 
 
use Drupal\Core\Routing\RouteMatchInterface;
 
 
/**
* Implements hook_help().
*/
function easydrupal_breadcrumb_help($route_name, RouteMatchInterface $route_match) {
 switch ($route_name) {
   // Main module help for the easydrupal_breadcrumb module.
   case 'help.page.easydrupal_breadcrumb':
     $output = '';
     $output .= '<h3>' . t('About') . '</h3>';
     $output .= '<p>' . t('Setting breadcrumbs for custom content types') . '</p>';
     return $output;
 
 
   default:
 }
}

services:
 easydrupal_breadcrumb.breadcrumb:
   class: Drupal\easydrupal_breadcrumb\Breadcrumb\EasydrupalBreadcrumbBuilder
   tags:
    - { name: breadcrumb_builder, priority: 100 }

<?php
 
 
namespace Drupal\easydrupal_breadcrumb\Breadcrumb;
 
 
use Drupal\Core\Breadcrumb\Breadcrumb;
use Drupal\Core\Breadcrumb\BreadcrumbBuilderInterface;
use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\Core\Link;
 
 
class EasydrupalBreadCrumbBuilder implements BreadcrumbBuilderInterface {
 /**
  * {@inheritdoc}
  */
 public function applies(RouteMatchInterface $attributes) {
   $parameters = $attributes->getParameters()->all();
   // I need my breadcrumbs for a few node types ONLY,
   // so it should be applied on node page ONLY.
   if (isset($parameters['node']) && !empty($parameters['node'])) {
     return TRUE;
   }
 }
 
 
 /**
  * {@inheritdoc}
  */
 public function build(RouteMatchInterface $route_match) {
   $breadcrumb = new Breadcrumb();
   $breadcrumb->addLink(Link::createFromRoute('Home', '<front>'));
 
   $node = \Drupal::routeMatch()->getParameter('node');
   $node_type = $node->bundle();
 
   switch ($node_type) {
     // If node type is "project"
     // I want to add as parent of breadcrumb my summary projects view.
     case 'project':
       $breadcrumb->addLink(Link::createFromRoute('Projects', 'view.portfolio.page_1'));
 
       break;
 
     // If node type is "article".
     // I want to add as parent of breadcrumb my summary articles view.
     case 'article':
       $breadcrumb->addLink(Link::createFromRoute('Articles', 'view.articles.page_1'));
 
       break;
   }
 
   // Don't forget to add cache control by a route,
   // otherwise you will surprice,
   // all breadcrumb will be the same for all pages.
   $breadcrumb->addCacheContexts(['route']);
 
   return $breadcrumb;
 }
 
}