8000 Document how to use named aliases by greg0ire · Pull Request #11339 · symfony/symfony-docs · GitHub
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Apr 9, 2019
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Document how to use named aliases #11339

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Document how to use named aliases
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@greg0ire
greg0ire committed Apr 9, 2019
commit c316951bbad04d61e2eb3b143c3d463a7935d613
65 changes: 59 additions & 6 deletions service_container/autowiring.rst
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Expand Up @@ -363,9 +363,40 @@ If you register this as a service, you now have *two* services that implement th
which one to use. Remember, autowiring isn't magic; it looks for a service
whose id matche 8000 s the type-hint. So you need to choose one by creating an alias
from the type to the correct service id (see :ref:`autowiring-interface-alias`).
Additionally, you can define several named aliases if you want to use
one implementation in some cases, and another implementation in some
other cases.

If you want ``Rot13Transformer`` to be the service that's used for autowiring, create
that alias:

For instance, you may want to use by default the ``Rot13Transformer``
implementation by default when the ``TransformerInterface`` interface is
type hinted, but use the ``UppercaseTransformer`` implementation in some
specific cases. To do so, you can create a normal alias from the
``TransformerInterface`` interface to ``Rot13Transformer``, and then
create a *named alias* from a special string containing the interface
followed by a variable name matching the one you use when doing the
injection::

namespace App\Service;

use App\Util\TransformerInterface;

class MastodonClient
{
private $transformer;

public function __construct(TransformerInterface $shoutyTransformer)
{
$this->transformer = $shoutyTransformer;
}

public function toot($user, $key, $status)
{
$transformedStatus = $this->transformer->transform($status);

// ... connect to Mastodon and send the transformed status
}
}

.. configuration-block::

Expand All @@ -378,15 +409,22 @@ that alias:
App\Util\Rot13Transformer: ~
App\Util\UppercaseTransformer: ~

# the ``App\Util\Rot13Transformer`` service will be injected when
# a ``App\Util\TransformerInterface`` type-hint is detected
# the ``App\Util\UppercaseTransformer`` service will be
# injected when an ``App\Util\TransformerInterface``
# type-hint for a ``$shoutyTransformer`` argument is detected.
App\Util\TransformerInterface: '@App\Util\Rot13Transformer'

# If the argument used for injection does not match, but the
# type-hint still matches, the ``App\Util\Rot13Transformer``
# service will be injected.
App\Util\TransformerInterface $shoutyTransformer: '@App\Util\UppercaseTransformer'

App\Service\TwitterClient:
# the Rot13Transformer will be passed as the $transformer argument
autowire: true

# If you wanted to choose the non-default service, wire it manually
# If you wanted to choose the non-default service and
# do not want to use a named alias, wire it manually
# arguments:
# $transformer: '@App\Util\UppercaseTransformer'
# ...
Expand All @@ -405,6 +443,9 @@ that alias:
<service id="App\Util\UppercaseTransformer"/>

<service id="App\Util\TransformerInterface" alias="App\Util\Rot13Transformer"/>
<service
id="App\Util\TransformerInterface $shoutyTransformer"
alias="App\Util\UppercaseTransformer"/>

<service id="App\Service\TwitterClient" autowire="true">
<!-- <argument key="$transformer" type="service" id="App\Util\UppercaseTransformer"/> -->
Expand All @@ -418,21 +459,33 @@ that alias:
use App\Util\Rot13Transformer;
use App\Util\UppercaseTransformer;
use App\Util\TransformerInterface;
use App\Service\MastodonClient;
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Alpha order

use App\Service\TwitterClient;

// ...
$container->autowire(Rot13Transformer::class);
$container->autowire(UppercaseTransformer::class);
$container->setAlias(TransformerInterface::class, Rot13Transformer::class);
$container->setAlias(
TransformerInterface::class.' $shoutyTransformer',
UppercaseTransformer::class
);
$container->autowire(TwitterClient::class)
//->setArgument('$transformer', new Reference(UppercaseTransformer::class))
;
$container->autowire(MastodonClient::class);

Thanks to the ``App\Util\TransformerInterface`` alias, any argument type-hinted
with this interface will be passed the ``App\Util\Rot13Transformer`` service.
But, you can also manually wire the *other* service by specifying the argument
If the argument is named ``$shoutyTransformer``,
``App\Util\UppercaseTransformer`` will be used instead.
But, you can also manually wire any *other* service by specifying the argument
under the arguments key.

.. versionadded:: 4.2

Named aliases have been introduced in Symfony 4.2.

46D5 Fixing Non-Autowireable Arguments
---------------------------------

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