Drupal7 to Drupal 8 changes

Drupal 7: example.info
name = Example
description = An example module.
core = 7.x
files[] = example.test
dependencies[] = user


 Drupal 8: example.info.yml
name: Example
description: An example module.
core: 8.x
dependencies: - user
# Note: New property required as of Drupal 8!
type: module

Creating MENU

Drupal 7: hook_menu()

example.module
<?php
/**
 * Implements hook_menu().
 */
function example_menu() {
 $items['hello'] = array(
 'title' => 'Hello world',
 'page callback' => '_example_page',
 'access callback' => 'user_access',
 'access arguments' => 'access content',
 'type' => MENU_CALLBACK,
 );
 return $items;
}
/**
 * Page callback: greets the user.
 */
function _example_page() {
 return array('#markup’ => t('Hello world.'));
}

?>


Drupal 8: Routes + Controllers

example.routing.yml

/* note: modulename.filepurpose , modulename is required next purpose can be anything which is understandable  */
example.controller:                   
 path: '/hello'                                          /* the path which will be used to display output  */
 defaults:
 _content: '\Drupal\example\Controller\Hello::content'     /* controller with class hello and method content  */
 requirements:
 _permission: 'access content'


Note: In route file 


src/Controller/Hello.php              /* the file name has to be same as class name used */

<?php
namespace Drupal\example\Controller;                 /* same as defined in yml _content */
use Drupal\Core\Controller\ControllerBase;         /* required to use controller */
/
**
 * Greets the user.
 */

class Hello extends ControllerBase {

 public function content() {                                        /* function name defined in yml */
 return array('#markup' => $this->t('Hello world.'));
 }
}
?>

Creating MENU with argument in url

route yml

modulename.controller_argument:

  path: '/example/{nodeID}'

  defaults:

    _controller: 'Drupal\modulename\Controller\Hello::getargument'

  requirements:

    _permission: 'access content'

<?php
namespace Drupal\example\Controller;                 /* same as defined in yml _content */
use Drupal\Core\Controller\ControllerBase;         /* required to use controller */
/
**
 * Greets the user.
 */

class Hello extends ControllerBase {

  public function getargument($nodeID) {

   return array(

      '#markup' => $nodeID,

    );

  }

}
?>