30_Middleware.md

SEO MetaData Middleware

Sometimes an extractor may need some more tools to create meta data. For example, the Schema Bundle allows you to use the fancy graph builder while creating schema blocks!

Adding Middleware

# app/config/services.yml
services:

    AppBundle\Seo\Middleware\MyCustomAdapter:
        tags:
            - { name: seo.meta_data.middleware.adapter, identifier: my_custom_adapter }

<?php

namespace AppBundle\Seo\Middleware;

use SeoBundle\Middleware\MiddlewareAdapterInterface;
use SeoBundle\Model\SeoMetaDataInterface;

class MyCustomAdapter implements MiddlewareAdapterInterface
{
    /**
     * @var string
     */
    protected $string;

    /**
     * {@inheritDoc}
     */
    public function boot()
    {
        $this->string = 'Important string!';
    }

    /**
     * {@inheritDoc}
     */
    public function getTaskArguments(): array
    {
        return [$this->string];
    }

    /**
     * {@inheritDoc}
     */
    public function onFinish(SeoMetaDataInterface $seoMetadata)
    {
        // nothing to do by default
        // in some extended usages you may want to finalize and add some data to the SeoMetaData object after all extractors have been dispatched.
    }
}

Usage

In your extractor you could use it like this:

<?php

namespace AppBundle\MetaData\Extractor;

use SeoBundle\MetaData\Extractor\ExtractorInterface;
use SeoBundle\Model\SeoMetaDataInterface;

class MyCustomExtractor implements ExtractorInterface
{
    /**
     * {@inheritdoc}
     */
    public function supports($element)
    {
        return $element instanceof MyClass;
    }

    /**
     * {@inheritdoc}
     * @throws \Exception
     */
    public function updateMetaData($element, ?string $locale, SeoMetaDataInterface $seoMetadata)
    {
        $middleware = $seoMetadata->getMiddleware('my_custom_adapter');
        $middleware->addTask(function (SeoMetaDataInterface $seoMetadata, string $string) {
            $seoMetadata->setTitle($string); // output: "Important string"
        });
    }
}