Programmatically use token filter

Question

I'm attempting to use the token filter programmatically inside a .theme file like so.

function mytheme_preprocess_block(&$vars){
  $token = Drupal::token();
  $vars['label'] = $token->replace('[node:title]');
}

I looked at https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21Utility%21Token.php/function/Token%3A%3Areplace/8.2.x for information. However when I output $vars['label'] all it produces is [node:title] as if no replacement occurred at all. How would I programmatically initiate the token filter?

UPDATE: As a test I attempted using another method of token to make sure anything was happening at all by using $token->scan('[node:title]'); and it did spit out

array(1) { ["node"]=> array(1) { ["title"]=> string(12) "[node:title]" } }

So I know I invoked the token class properly at least

UPDATE: It appears that the token replace was working it just didn't recognize [node:title]. Using [site:name] did produce the expected result. How would I be able to get [node:title] to work? Do I need to supply it with that data?

Answer 1

Data about the node needed to be supplied as a parameter to the replace method. It worked once I used

$node = \Drupal::routeMatch()->getParameter('node');
$vars['label'] = $token->replace($vars['label'],['node' => $node]);