How can I make Craft's caching aware of fields used inside a plugin?

Question

I have a complex template which uses various modules and sub-components for which I opted for handling all the logic and rendering directly in PHP, as it felt like it was too complex a job for twig.

Currently, when I change a field (e.g. swap out an image) inside one of the modules, the surrounding cache isn't busted, so the site doesn't update.

My question is: How can I make Craft aware of fields used inside a plugin within a {% cache %} tag, so that when a field is changed, the surrounding cache is busted?

I am aware of the TemplateCacheService, but unsure if / how I can use that in this case (I had a bit of an experiment with no success).

The modules represent a Neo field, but my assumption is that this would work very similarly if not identically to if this was a matrix field.

 

A super-reduced test case looks something like the following:

{% for module in modules %}
    {% cache using key module.id %}
        {{ craft.control.renderModule(module) }}
    {% endcache %}
{% endfor %}

_modules.twig

 

<?php

namespace Craft;

class ControlVariable
{

    public function renderModule($module)
    {
        return craft()->control_modules->renderModule($module);
    }
}

ControlVariable.php

 

<?php

namespace Craft;

class Control_ModulesService extends BaseApplicationComponent
{

public function __construct()
{}

public function renderModule($module)
{
    ?>

    <!-- How can Craft know when this image changes? -->
    <img src="<?= $module->myImageField->first()->getUrl(); ?>">

    <?php
}

Control_ModulesService.php

 

FWIW, in the following setup, the cache is successfully busted when changing the image field in the CMS:

{% for module in modules %}
    {% cache using key module.id %}
        <img src="{{ module.myImageField.first().getUrl() }}">      
    {% endcache %}
{% endfor %}

_modules.twig

Answer 1

The {% cache %} tag tracks Elements (Users, Entries, Categories, Tags, etc.), so if you're want to do this using a plugin, then the plugin's field type needs to inherit from BaseElementFieldType and needs to implement its own element type.

From there, it's just a matter of calling craft()->templateCache->includeElementInTemplateCaches().