Talk TYPO3 Dependency Injection
===============================

A practical introduction into Dependency Injection with Symfony Dependency Injection for TYPO3.

.. contents::
   :local:

What is Dependency Injection
----------------------------

- Our code has dependencies (E.g. Controller → View, Controller → Repository)

- Inversion of control (ask others to inject dependencies)

- Allow configuration of dependencies

- Do yourself a favour and use interfaces

- Used to connect pieces of code (E.g. event listener, commands, …)

Flow
----

TYPO3 will:

1. Check all ``Services.yaml`` and ``Services.php`` files once

2. Use Symfony Dependency Injection once

3. To build a psr/container (PSR-11) once

4. Then load the psr/container on consecutive calls

5. Use psr/container to fetch concrete implementations

The generated code (Container) is stored at:
``var/cache/code/di/DependencyInjectionContainer_<hash>.php``

Usage within TYPO3
------------------

Injection
^^^^^^^^^

A consumer needs dependencies.

- Injection via ``__construct()``

- Injection via ``inject*()`` method

- Injection via ``@required`` annotated method

See: https://docs.typo3.org/m/typo3/reference-coreapi/main/en-us/ApiOverview/DependencyInjection/Index.html#constructor-injection

Manually create instances
^^^^^^^^^^^^^^^^^^^^^^^^^

Always use ``GeneralUtility::makeInstance()``.

- 0 arguments will ask the container

- Requested service needs to be public

Public services
^^^^^^^^^^^^^^^

Prevent them!

Mark as public when TYPO3 forces you to do so.

See: https://docs.typo3.org/m/typo3/reference-coreapi/main/en-us/ApiOverview/DependencyInjection/Index.html#what-to-make-public

The Services.yaml
-----------------

Basic example if you prefer YAML:

.. code-block:: yaml
   :linenos:

   services:
    _defaults:
      autowire: true
      autoconfigure: true
      public: false

    DanielSiepmann\Tracking\:
      resource: '../Classes/*'

The Services.php
-----------------

Basic example if you prefer PHP:

.. code-block:: php
   :linenos:

   <?php

   declare(strict_types=1);

   namespace WerkaumMedia\ABTest\Configuration;

   use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;

   return static function (
      ContainerConfigurator $containerConfigurator
   ) {
       $services = $containerConfigurator
           ->services()
           ->defaults()
           ->autowire()
           ->autoconfigure()
       ;

       $services->load('WerkraumMedia\\ABTest\\', '../Classes/');
   };

Concrete Examples
-----------------

Injecting Query Builder
^^^^^^^^^^^^^^^^^^^^^^^

.. code-block:: yaml
   :linenos:

   services:
     _defaults:
       autowire: true
       autoconfigure: true
       public: false

     DanielSiepmann\Tracking\:
       resource: '../Classes/*'

     querybuilder.tx_tracking_pageview:
       class: 'TYPO3\CMS\Core\Database\Query\QueryBuilder'
       factory:
         - '@TYPO3\CMS\Core\Database\ConnectionPool'
         - 'getQueryBuilderForTable'
       arguments:
         - 'tx_tracking_pageview'

     DanielSiepmann\Tracking\Domain\Repository\Pageview:
       public: true
       arguments:
         - '@querybuilder.tx_tracking_pageview'

See: https://git.daniel-siepmann.de/danielsiepmann/tracking/src/branch/main/Configuration/Services.yaml

Event Listener
^^^^^^^^^^^^^^

.. code-block:: php
   :linenos:

   <?php

   declare(strict_types=1);

   namespace WerkraumMedia\ABTest\Configuration;

   use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;
   use WerkraumMedia\ABTest\Events\SwitchedToVariant;
   use WerkraumMedia\ABTest\MatomoTracker;

   return static function (ContainerConfigurator $containerConfigurator) {
       $services = $containerConfigurator
           ->services()
           ->defaults()
           ->autowire()
           ->autoconfigure()
       ;

       $services->load('WerkraumMedia\\ABTest\\', '../Classes/');

       $services->set(MatomoTracker::class)->tag('event.listener', [
           'method' => 'handleVariant',
           'event' => SwitchedToVariant::class,
       ]);
   };

See: https://git.daniel-siepmann.de/Customers/abtest/src/branch/main/Configuration/Services.php

Command
^^^^^^^

.. code-block:: php
   :linenos:

   services:
     _defaults:
       autowire: true
       autoconfigure: true
       public: false

     DanielSiepmann\Tracking\:
       resource: '../Classes/*'

     DanielSiepmann\Tracking\Command\UpdateDataCommand:
       tags:
         - name: 'console.command'
           command: 'tracking:updatedata'

See: https://git.daniel-siepmann.de/danielsiepmann/tracking/src/branch/main/Configuration/Services.yaml

CompilerPass
------------

- Alter existing service definitions

- E.g. add tagged classes to a registry

- E.g. add event listeners

- E.g. mark classes as public

.. code-block:: php
   :linenos:

   <?php

   declare(strict_types=1);

   namespace WerkraumMedia\ThueCat;

   use Symfony\Component\DependencyInjection\ContainerBuilder;
   use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;
   use WerkraumMedia\ThueCat\Domain\Import\Entity\MapsToType;
   use WerkraumMedia\ThueCat\Domain\Import\Typo3Converter\Converter;
   use WerkraumMedia\ThueCat\Domain\Import\UrlProvider\UrlProvider;

   return function (ContainerConfigurator $container, ContainerBuilder $containerBuilder) {
       $containerBuilder->registerForAutoconfiguration(UrlProvider::class)
         ->addTag(DependencyInjection\UrlProvidersPass::TAG);
       $containerBuilder->addCompilerPass(new DependencyInjection\UrlProvidersPass());

       $containerBuilder->registerForAutoconfiguration(Converter::class)
         ->addTag(DependencyInjection\ConverterPass::TAG);
       $containerBuilder->addCompilerPass(new DependencyInjection\ConverterPass());

       $containerBuilder->registerForAutoconfiguration(MapsToType::class)
         ->addTag(DependencyInjection\EntityPass::TAG);
       $containerBuilder->addCompilerPass(new DependencyInjection\EntityPass());
   };

   .. code-block:: php
      :linenos:

   <?php

   declare(strict_types=1);

   namespace WerkraumMedia\ThueCat\DependencyInjection;

   use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
   use Symfony\Component\DependencyInjection\ContainerBuilder;
   use WerkraumMedia\ThueCat\Domain\Import\Typo3Converter\Registry;

   class ConverterPass implements CompilerPassInterface
   {
       public const TAG = 'thuecat.typo3.converter';

       public function process(ContainerBuilder $container): void
       {
           $registry = $container->findDefinition(Registry::class);

           foreach ($container->findTaggedServiceIds(self::TAG) as $id => $tags) {
               $definition = $container->findDefinition($id);
               if (!$definition->isAutoconfigured() || $definition->isAbstract()) {
                   continue;
               }

               $registry->addMethodCall('registerConverter', [$definition]);
           }
       }
   }

See:

- https://git.daniel-siepmann.de/Customers/thuecat/src/branch/main/Configuration/Services.php

- https://git.daniel-siepmann.de/Customers/thuecat/src/branch/main/Classes/DependencyInjection

- https://symfony.com/doc/current/service_container/compiler_passes.html

Sources
-------

- https://docs.typo3.org/m/typo3/reference-coreapi/main/en-us/ApiOverview/DependencyInjection/Index.html

- https://symfony.com/doc/current/components/dependency_injection.html

- https://symfony.com/doc/current/service_container.html

- https://usetypo3.com/dependency-injection.html

- https://usetypo3.com/di-and-events-example.html

- https://daniel-siepmann.de/concrete-typo3-dependency-injection-examples.html

- https://daniel-siepmann.de/prepare-legacy-code-for-upcoming-typo3-versions.html

- https://en.wikipedia.org/wiki/Dependency_injection

- https://www.php-fig.org/psr/psr-11/