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feat(DI): static injection
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‎components/phpunit_bridge.rst

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@@ -621,7 +621,7 @@ toggle a behavior::
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public function hello(): string
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{
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if (class_exists(DependencyClass::class)) {
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return 'The dependency bahavior.';
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return 'The dependency behavior.';
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}
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return 'The default behavior.';
@@ -639,7 +639,7 @@ are installed during tests) would look like::
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public function testHello()
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{
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$class = new MyClass();
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$result = $class->hello(); // "The dependency bahavior."
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$result = $class->hello(); // "The dependency behavior."
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// ...
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}
@@ -663,7 +663,7 @@ classes, interfaces and/or traits for the code to run::
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ClassExistsMock::withMockedClasses([DependencyClass::class => false]);
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$class = new MyClass();
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$result = $class->hello(); // "The default bahavior."
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$result = $class->hello(); // "The default behavior."
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// ...
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}

‎routing.rst

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@@ -431,7 +431,6 @@ defined as ``/blog/{slug}``:
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<route id="blog_show" path="/blog/{slug}"
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controller="App\Controller\BlogController::show"/>
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</route>
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</routes>
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.. code-block:: php
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<route id="blog_show" path="/blog/{slug}"
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controller="App\Controller\BlogController::show"/>
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</route>
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</routes>
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.. code-block:: php

‎service_container/calls.rst

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@@ -77,3 +77,80 @@ To configure the container to call the ``setLogger`` method, use the ``calls`` k
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->call('setLogger', [ref('logger')]);
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};
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.. versionadded:: 4.3
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The ``immutable-setter`` injection was introduced in Symfony 4.3.
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In order to provide immutable services, some classes implement immutable setters.
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Such setters return a new instance of the configured class
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instead of mutating the object they were called on::
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namespace App\Service;
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use Psr\Log\LoggerInterface;
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class MessageGenerator
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{
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private $logger;
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/**
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* @return static
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*/
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public function withLogger(LoggerInterface $logger)
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{
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$new = clone $this;
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$new->logger = $logger;
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return $new;
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}
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// ...
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}
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Because the method returns a separate cloned instance, configuring such a service means using
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the return value of the wither method (``$service = $service->withLogger($logger);``).
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The configuration to tell the container it should do so would be like:
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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\Service\MessageGenerator:
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# ...
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calls:
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- method: withLogger
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arguments:
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- '@logger'
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returns_clone: true
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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="https://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\Service\MessageGenerator">
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<!-- ... -->
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<call method="withLogger" returns-clone="true">
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<argument type="service" id="logger" />
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</call>
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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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use App\Service\MessageGenerator;
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use Symfony\Component\DependencyInjection\Reference;
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$container->register(MessageGenerator::class)
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->addMethodCall('withLogger', [new Reference('logger')], true);

‎service_container/definitions.rst

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@@ -117,6 +117,9 @@ any method calls in the definitions as well::
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// configures a new method call
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$definition->addMethodCall('setLogger', [new Reference('logger')]);
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// configures an immutable-setter
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$definition->addMethodCall('withLogger', [new Reference('logger')], true);
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// replaces all previously configured method calls with the passed array
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$definition->setMethodCalls($methodCalls);
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‎service_container/injection_types.rst

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@@ -105,6 +105,112 @@ working with optional dependencies. It is also more difficult to use in
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combination with class hierarchies: if a class uses constructor injection
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then extending it and overriding the constructor becomes problematic.
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Immutable-setter Injection
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--------------------------
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.. versionadded:: 4.3
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The ``immutable-setter`` injection was introduced in Symfony 4.3.
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Another possible injection is to use a method which returns a separate instance
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by cloning the original service, this approach allows you to make a service immutable::
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// ...
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use Symfony\Component\Mailer\MailerInterface;
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class NewsletterManager
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{
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private $mailer;
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/**
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* @required
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* @return static
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*/
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public function withMailer(MailerInterface $mailer)
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{
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$new = clone $this;
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$new->mailer = $mailer;
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return $new;
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}
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// ...
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}
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In order to use this type of injection, don't forget to configure it:
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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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# ...
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app.newsletter_manager:
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class: App\Mail\NewsletterManager
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calls:
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- [withMailer, ['@mailer'], true]
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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="https://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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<!-- ... -->
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<service id="app.newsletter_manager" class="App\Mail\NewsletterManager">
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<call method="withMailer" returns-clone="true">
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<argument type="service" id="mailer" />
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</call>
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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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use App\Mail\NewsletterManager;
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use Symfony\Component\DependencyInjection\Reference;
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// ...
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$container->register('app.newsletter_manager', NewsletterManager::class)
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->addMethodCall('withMailer', [new Reference('mailer')], true);
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.. note::
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If you decide to use autowiring, this type of injection requires
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that you add a ``@return static`` docblock in order for the container
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to be capable of registering the method.
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This approach is useful if you need to configure your service according to your needs,
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so, here's the advantages of immutable-setters:
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* Immutable setters works with optional dependencies, this way, if you don't need
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a dependency, the setter don't need to be called.
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* Like the constructor injection, using immutable setters force the dependency to stay
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the same during the lifetime of a service.
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* This type of injection works well with traits as the service can be composed,
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this way, adapting the service to your application requirements is easier.
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* The setter can be called multiple times, this way, adding a dependency to a collection
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becomes easier and allows you to add a variable number of dependencies.
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The disadvantages are:
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* As the setter call is optional, a dependency can be null during execution,
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you must check that the dependency is available before calling it.
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* Unless the service is declared lazy, it is incompatible with services
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that reference each other in what are called circular loops
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Setter Injection
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----------------
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the method adds the dependency to a collection. You can then have a variable
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number of dependencies.
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* Like the immutable-setter one, this type of injection works well with
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traits and allows you to compose your service.
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The disadvantages of setter injection are:
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* The setter can be called more than just at the time of construction so
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But, it is useful to know that this can be done with the service container,
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especially if you are working with code that is out of your control, such
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as in a third party library, which uses public properties for its dependencies.
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Immutable Injection
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-------------------
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Another possible injection in to use a method which return ``static``,
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this approach allow you to make a service immutable::
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// ...
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class NewsletterManager
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{
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private $mailer;
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/**
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* @required
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* @return static
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*/
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public function withMailer(MailerInterface $mailer)
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{
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$new = clone $this;
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$new->mailer = $mailer;
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return $new;
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}
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// ...
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}
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In order to use the full potential of this approach, you can define a third argument
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which allow the container to return the newly created service:
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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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# ...
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app.newsletter_manager:
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class: App\Mail\NewsletterManager
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calls:
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- [withMailer, ['@mailer'], true]
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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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http://symfony.com/schema/dic/services/services-1.0.xsd">
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<services>
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<!-- ... -->
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<service id="app.newsletter_manager" class="App\Mail\NewsletterManager">
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<call method="withMailer" use-result=true>
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<argument type="service" id="mailer" />
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</call>
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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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use App\Mail\NewsletterManager;
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use Symfony\Component\DependencyInjection\Reference;
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// ...
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$container->register('app.newsletter_manager', NewsletterManager::class)
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->addMethodCall('withMailer', [new Reference('mailer')], true);
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.. note::
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This type of injection requires that you add a ``@return static`` docblock in order
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for the container to be capable of registering the method.
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This approach is useful if you need to configure your service according to your needs,
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so, what are the advantages?
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* Your service becomes immutable, as the container will return a new object,
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the initial service stays clean and unchanged.
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* You can easily change the injected service as long as it respect the interface/type
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asked by the initial service.
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* It allow you to get rid of factory usages which can lead a more complex code
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* As the dependency is optional, you can easily decide to receive the service
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without using the "with" method.
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* As the method automatically receive and set the attribute value,
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you couldn't obtain the newly created service without this dependency.
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The disadvantages are:
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* As the ``@return static`` docblock is required by the container to
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understand that the method return a new object,
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you can found that adding docblock for a single method isn't adapted or
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link your code to the container.
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* As this approach force the container to create a new object
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once the method is called, you can found hard to debug and test your code.

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