Can't access controller from element

Question

I am trying to use content filled from a controller inside an element so I can use the content to build a view.

So far I have the following element (.ctp file)

<?php $categories = $this->requestAction('categories/menu'); ?>

<ul class="hidden">
    <?php foreach ($categories as $categorie): ?>
    <li><?= $this->Html->link($categorie->name, '#'); ?></li>
    <?php endforeach; ?>
</ul>

with this controller

class CategoriesController extends AppController
{
    public function index()
    {
        $categories = $this->Categories->find('all');
        $this->set(compact('categories'));
    }

    public function menu()
    {
        $categories = $this->paginate();
        $this->set('categories', $categories);
    }
}

When using the code from here I got an error in the log and nothing display on the page Error: [Cake\View\Exception\MissingTemplateException] Template file "Categories\menu.ctp" is missing. .

If I change this ligne $this->set('categories', $categories);for this one return $categories; I have the following error displaying on my page Error: Controller action can only return an instance of Response.

I originally tryed the code from this tutorial (sorry for the scrolling just go to the last example before Caching Elements) but it lead to the second error message.

How can I use a Controller from an Element?

Answer 1

This is the expected behavior, a controller needs a view template to render unless you explicitly disabled/circumvent view rendering by either setting Controller::$autoRender to false, by making the method return a Response object, or by using serialized data views.

The latter is what the error message tells you the method is expected to return, see http://book.cakephp.org/3.0/en/controllers.html#controller-actions

When you use controller methods with Routing\RequestActionTrait::requestAction() you will typcially return a Response instance. If you have controller methods that are used for normal web requests + requestAction, you should check the request type before returning

// src/Controller/RecipesController.php

class RecipesController extends AppController
{
    public function popular()
    {
       $popular = $this->Recipes->find('popular');
        if (!$this->request->is('requested')) {
            $this->response->body(json_encode($popular));
            return $this->response;
        }
        $this->set('popular', $popular);
    }
}

[...]

View cells

As it looks like you just want to fetch and render model data, I'd suggest to check out view cells.

http://book.cakephp.org/3.0/en/views/cells.html