#type
#cache
#markup
#prefix/#suffix
#pre_render
#post_render
#theme
#theme_wrappers

Example:

Exemple 1 : Form with Node

in routing.yml

my.node.info:

  path: '/user/contactmail/{node}'

  defaults:

    _form: '\Drupal\myx_meet\Form\ContactUserForm'

    _title: 'Contact'



Methode 1 : Example:

$value = $node->get($field)->value;

$target = $node->get($field)->target_id; // For entity ref

Methode 2 Example:

Example:

$node = \Drupal::routeMatch()->getParameter('node');

if ($node) {

  $nid = $node->id();

}