.. include:: /Includes.rst.txt .. _DependencyInjection: ==================== Dependency Injection ==================== .. versionadded:: 10.0 :doc:`Changelog/10.0/Feature-84112-SymfonyDependencyInjectionForCoreAndExtbase` TYPO3 uses a Dependency Injection solution based on the corresponding `PSR-11 `_ compliant Symfony component to standardize object initialization throughout the core as well as in extensions. The recommended way of injecting dependencies is to use constructor injection:: public function __construct(Dependency $dependency) { $this->dependency = $dependency; } By default all classes shipped by the TYPO3 core system extensions are available for dependency injection. .. contents:: :depth: 3 .. _configure-dependency-injection-in-extensions: Configure Dependency Injection in Extensions ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Extensions have to configure their classes to make use of the dependency injection. This can be done in :file:`Configuration/Services.yaml`. Alternatively :file:`Configuration/Services.php` can be used. .. code-block:: yaml # Configuration/Services.yaml services: _defaults: autowire: true autoconfigure: true public: false Your\Namespace\: resource: '../Classes/*' This is how a basic :file:`Services.yaml` of an extension looks like. The meaning of :yaml:`autowire`, :yaml:`autoconfigure` and :yaml:`public` will be explained below. .. note:: Whenever service configuration or class dependencies change, the Core cache needs to be flushed in the Install Tool to rebuild the compiled Symfony container. Flushing all caches from the cache clear menu does not flush the compiled Symfony container. .. _autowire: Autowire -------- :yaml:`autowire: true` instructs the dependency injection component to calculate the required dependencies from type declarations. This works for constructor and inject methods. The calculation yields to a service initialization recipe which is cached in php code (in TYPO3 core cache). .. note:: An extension doesn't need to use autowiring, it is free to manually wire dependencies in the service configuration file. Autoconfigure ------------- It is suggested to enable :yaml:`autoconfigure: true` as this will automatically add Symfony service tags based on implemented interfaces or base classes. For example autoconfiguration ensures that classes which implement :php:`\TYPO3\CMS\Core\SingletonInterface` will be publicly available from the Symfony container. Arguments --------- In case you turned autowire off or need special arguments set, you can configure those as well. This means you could set :yaml:`autowire: false` for an extension but provide the needed arguments via config specifically for classes you want to. This can be done in chronological order or by naming them. .. code-block:: yaml # Configuration/Services.yaml Vendor\MyExtension\UserFunction\ClassA: arguments: $argA: '@TYPO3\CMS\Core\Database\ConnectionPool' Vendor\MyExtension\UserFunction\ClassB: arguments: - '@TYPO3\CMS\Core\Database\ConnectionPool' This enables you to inject concrete objects like the QueryBuilder or Database Connection: .. code-block:: yaml # Configuration/Services.yaml querybuilder.pages: class: 'TYPO3\CMS\Core\Database\Query\QueryBuilder' factory: - '@TYPO3\CMS\Core\Database\ConnectionPool' - 'getQueryBuilderForTable' arguments: - 'pages' Vendor\MyExtension\UserFunction\ClassA: public: true arguments: - '@querybuilder.pages' Now you can access the QueryBuilder instance within ClassA. With this you can call your queries without further instantiation. Be aware to clone your object or resetting the query parts to prevent side effects in case of multiple usages. This method of injecting Objects does also work with e.g. extension configurations or typoscript settings. Public ------ :yaml:`public: false` is a performance optimization and is therefore suggested to be set in extensions. This settings controls which services are available through the dependency injection container which is used internally by :php:`GeneralUtility::makeInstance()`. However some classes that need to be public will be marked public automatically due to :yaml:`autoconfigure: true`. These classes include singletons, because they need to be shared with code that uses :php:`GeneralUtility::makeInstance()` and Extbase controllers. .. _knowing-what-to-make-public: Knowing what to make public ^^^^^^^^^^^^^^^^^^^^^^^^^^^ .. The following indent is intentional to create a blockquote: .. "Simply said: A service can be marked as private if you do not want to access it directly from your code." -- `Symfony official documentation `_ for public and private services. Direct access includes instantiation via :php:`GeneralUtility::makeInstance()` with constructor arguments. This means every class that needs dependency injection and is retrieved directly, e.g. using :php:`GeneralUtility::makeInstance()` must be marked as public. Any other class which needs dependency injection and is retrieved by dependency injection itself can be private. Instances of :php:`\TYPO3\CMS\Core\SingletonInterface` and Extbase controllers are automatically marked as public because they are retrieved using :php:`GeneralUtility::makeInstance()`. More examples for classes which must be marked as public: * User functions * Non-Extbase controllers * Classes registered in hooks * Authentication services * Fluid data processors For such classes an extension can override the global :yaml:`public: false` configuration in the :file:`Configuration/Services.yaml` for each affected class. .. code-block:: yaml # Configuration/Services.yaml services: _defaults: autowire: true autoconfigure: true public: false Vendor\MyExtension\: resource: '../Classes/*' Vendor\MyExtension\UserFunction\ClassA: public: true With this configuration you can use dependency injection in :php:`\Vendor\MyExtension\UserFunction\ClassA` when it is created e.g. in the context of a :typoscript:`USER` TypoScript object which would not be possible if this class was private. .. _errors-resulting-from-wrong-configuration: Errors resulting from wrong configuration ----------------------------------------- When objects using dependency injection are not configured properly, one or more of the following issues can be the result. In such a case, check whether the class has to be configured as :yaml:`public: true`. :php:`ArgumentCountError` is raised on missing dependency injection for :ref:`constructor-injection`: .. code-block:: text (1/1) ArgumentCountError Too few arguments to function Vendor\ExtName\Namespace\Class::__construct(), 0 passed in typo3/sysext/core/Classes/Utility/GeneralUtility.php on line 3461 and exactly 1 expected An :php:`Error` is raised on missing dependency injection for :ref:`method-injection`, once the dependency is used within the code: .. code-block:: text (1/1) Error Call to a member function methodName() on null .. _supported-ways-of-dependency-injection: Supported Ways of Dependency Injection ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Classes should be adapted to avoid both, :php:`\TYPO3\CMS\Extbase\Object\ObjectManager` and :php:`\TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance()` whenever possible. Class dependencies should be injected via constructor injection or setter methods. .. _constructor-injection: Constructor Injection --------------------- A class dependency can simply be specified as a constructor argument:: public function __construct(Dependency $dependency) { $this->dependency = $dependency; } .. _method-injection: Method Injection ---------------- As an alternative to constructor injection :php:`injectDependency()` Methods can be used. Additionally a :php:`setDependency()` will also work if it has the annotation :php:`@required`:: /** * @param MyDependency $myDependency */ public function injectMyDependency(MyDependency $myDependency) { $this->myDependency = $myDependency; } /** * @param MyOtherDependency $myOtherDependency * @required */ public function setMyOtherDependency(MyOtherDependency $myOtherDependency) { $this->myOtherDependency = $myOtherDependency; } .. _interface-injection: Interface Injection ------------------- It is possible to inject interfaces as well. If there is only one implementation for a certain interface the interface injection is simply resolved to this implementation:: public function __construct(DependencyInterface $dependency) { $this->dependency = $dependency; } When multiple implementation of the same interface exist, an extension needs to specify which implementation should be injected when the interface is type hinted. Find out more about how this is achieved in the official `Symfony documentation `_. Further Information ^^^^^^^^^^^^^^^^^^^ * `Symfony dependency injection component `__ * `Symfony service container `_ * :doc:`ext_core:Changelog/10.0/Feature-84112-SymfonyDependencyInjectionForCoreAndExtbase` of the TYPO3 core.