10000 [DI] Document proxifying interfaces for lazy services · symfony/symfony-docs@f86b976 · GitHub
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[DI] Document proxifying interfaces for lazy services
Symfony 4.2 introduced the possibility to lazy load services using final classes by proxyfying specific interfaces, but this has not been documented yet.
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‎service_container/lazy_services.rst

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@@ -25,7 +25,8 @@ until you interact with the proxy in some way.
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.. caution::
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Lazy services do not support `final`_ classes.
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Lazy services do not support `final`_ classes. You can use `Interface
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Proxifying`_ to work around this limitation.
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Installation
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------------
@@ -97,6 +98,81 @@ To check if your proxy works you can check the interface of the received object:
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`ocramius/proxy-manager`_, the container will skip over the ``lazy``
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flag and directly instantiate the service as it would normally do.
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Interface Proxifying
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--------------------
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Under the hood, proxies generated to lazily load services inherit from the class
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used by the service. But sometimes this is not possible at all (`final`_ classes
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can not be extended for example) or not convenient.
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To workaround this limitation, you can configure a proxy to only implements
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specific interfaces.
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.. versionadded:: 4.2
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Proxyfying interfaces was introduced in Symfony 4.2.
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.. configuration-block::
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.. code-block:: yaml
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# config/services.yaml
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services:
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App\Twig\AppExtension:
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lazy: 'Twig\Extension\ExtensionInterface'
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# or a complete definition:
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lazy: true
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tags:
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- { name: 'proxy', interface: 'Twig\Extension\ExtensionInterface' }
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.. code-block:: xml
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<!-- config/services.xml -->
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<?xml version="1.0" encoding="UTF-8" ?>
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<container xmlns="http://symfony.com/schema/dic/services"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://symfony.com/schema/dic/services
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https://symfony.com/schema/dic/services/services-1.0.xsd">
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<services>
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<service id="App\Twig\AppExtension" lazy="Twig\Extension\ExtensionInterface"/>
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<!-- or a complete definition: -->
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<service id="App\Twig\AppExtension" lazy="true">
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<tag name="proxy" interface="Twig\Extension\ExtensionInterface"/>
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</service>
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</services>
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</container>
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.. code-block:: php
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// config/services.php
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namespace Symfony\Component\DependencyInjection\Loader\Configurator;
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use App\Twig\AppExtension;
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use Twig\Extension\ExtensionInterface;
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return function(ContainerConfigurator $configurator) {
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$services = $configurator->services();
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$services->set(AppExtension::class)
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->lazy()
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->tag('proxy', ['interface' => ExtensionInterface::class])
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;
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};
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The virtual `proxy`_ injected into other services will only implement the
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specified interfaces and will not extend the original service class allowing to
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lazy load service using `final`_ classes. You can configure the proxy to
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implement multiple interfaces by repeating the "proxy" tag.
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.. tip::
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This features can also act as a "safe guard". Because the proxy does not
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extends the original class, only the methods defined by the interfaces can
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be called, preventing to call implementation specific one. It also prevents
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injecting the dependency at all if you type hinted a concrete implementation
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instead of the interface.
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Additional Resources
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--------------------
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