How do you pass more than one node to a route?

Question

I am working on converting a drupal 7 site to drupal 8 for some practice with 8. In my drupal 7 site, I have a custom hook_menu declaration with the following:

function solution_menu() {
  $items = array();
  $items['solution/%node/%node/%node'] = array(
    'title' => '',
    'page callback' => 'solution_build_solution',
    'page arguments' => array(1,2,3),
    'access callback' => 1,
    'type' => MENU_CALLBACK,
  );
  return $items;
}

function solution_build_solution($solution_node, $species_node, $problem_node) {
   //build solution
}

I am trying to accomplish the same thing in drupal 8 with a route. However, if I try something like the following i get an error:

wlh_decision.solution:
  path: '/solution/{node}/{node}/{node}'
  defaults:
    _content: '\Drupal\wlh_decision\Controller\SolutionController::displaySolution'
    _title: 'Solution:'
    _title_callback: '\Drupal\wlh_decision\Controller\SolutionController::solutionTitle'
  requirements:
    _permission: 'access content'

The error i get is:

LogicException: Route pattern "/solution/{node}/{node}/{node}" cannot reference variable name "node" more than once. in Symfony\Component\Routing\RouteCompiler::compilePattern() (line 106 of /Users/brianwilliams/Sites/MAMP/drupal8/core/vendor/symfony/routing/Symfony/Component/Routing/RouteCompiler.php).

but if i change it to use names other than node, I don't get the autoloading.

Anybody know how I am able to handle this?

Answer 1

You can specify the upcast type for parameters manually:

wlh_decision.solution:
  path: '/solution/{solution_node}/{species_node}/{problem_node}'
  defaults:
    _content: '\Drupal\wlh_decision\Controller\SolutionController::displaySolution'
    _title: 'Solution:'
    _title_callback: '\Drupal\wlh_decision\Controller\SolutionController::solutionTitle'
  requirements:
    _permission: 'access content'
  options:
    parameters:
      solution_node:
        type: entity:node
      species_node:
        type: entity:node
      problem_node:
        type: entity:node

See Using parameters in routes for a slightly more in-depth explanation.