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Removed synchronized services from Symfony 2.7 docs
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javiereguiluz committed Apr 13, 2015
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How to Work with Scopes
=======================

This entry is all about scopes, a somewhat advanced topic related to the
This article is all about scopes, a somewhat advanced topic related to the
:doc:`/book/service_container`. If you've ever gotten an error mentioning
"scopes" when creating services, then this entry is for you.
"scopes" when creating services, then this article is for you.

.. note::

Expand All @@ -25,10 +25,11 @@ The scope of a service controls how long an instance of a service is used
by the container. The DependencyInjection component provides two generic
scopes:

- ``container`` (the default one): The same instance is used each time you
request it from this container.
``container`` (the default one):
The same instance is used each time you ask for it from this container.

- ``prototype``: A new instance is created each time you request the service.
``prototype``:
A new instance is created each time you ask for the service.

The
:class:`Symfony\\Component\\HttpKernel\\DependencyInjection\\ContainerAwareHttpKernel`
Expand All @@ -40,9 +41,9 @@ An Example: Client Scope
~~~~~~~~~~~~~~~~~~~~~~~~

Other than the ``request`` service (which has a simple solution, see the
above note), no services in the default Symfony2 container belong to any
above note), no services in the default Symfony container belong to any
scope other than ``container`` and ``prototype``. But for the purposes of
this entry, imagine there is another scope ``client`` and a service ``client_configuration``
this article, imagine there is another scope ``client`` and a service ``client_configuration``
that belongs to it. This is not a common situation, but the idea is that
you may enter and exit multiple ``client`` scopes during a request, and each
has its own ``client_configuration`` service.
Expand Down Expand Up @@ -71,7 +72,7 @@ when compiling the container. Read the sidebar below for more details.
called *ConfigurationA* here) is passed to it. Life is good!

* Your application now needs to do something with another client, and
you've architected your application in such a way that you handle this
you've designed your application in such a way that you handle this
by entering a new ``client_configuration`` scope and setting a new
``client_configuration`` service into the container. Call this
*ConfigurationB*.
Expand All @@ -96,169 +97,28 @@ when compiling the container. Read the sidebar below for more details.
Using a Service from a Narrower Scope
-------------------------------------

There are several solutions to the scope problem:
There are two solutions to the scope problem:

* A) Use setter injection if the dependency is ``synchronized`` (see
:ref:`using-synchronized-service`);

* B) Put your service in the same scope as the dependency (or a narrower one). If
* A) Put your service in the same scope as the dependency (or a narrower one). If
you depend on the ``client_configuration`` service, this means putting your
new service in the ``client`` scope (see :ref:`changing-service-scope`);

* C) Pass the entire container to your service and retrieve your dependency from
* B) Pass the entire container to your service and retrieve your dependency from
the container each time you need it to be sure you have the right instance
-- your service can live in the default ``container`` scope (see
:ref:`passing-container`).

Each scenario is detailed in the following sections.

.. _using-synchronized-service:

A) Using a Synchronized Service
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. versionadded:: 2.3
Synchronized services were introduced in Symfony 2.3.

Both injecting the container and setting your service to a narrower scope have
drawbacks. Assume first that the ``client_configuration`` service has been
marked as ``synchronized``:

.. configuration-block::

.. code-block:: yaml
# app/config/config.yml
services:
client_configuration:
class: AppBundle\Client\ClientConfiguration
scope: client
synchronized: true
synthetic: true
# ...
.. code-block:: xml
<!-- app/config/config.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://symfony.com/schema/dic/services
http://symfony.com/schema/dic/services/services-1.0.xsd"
>
<services>
<service
id="client_configuration"
scope="client"
synchronized="true"
synthetic="true"
class="AppBundle\Client\ClientConfiguration"
/>
</services>
</container>
.. code-block:: php
// app/config/config.php
use Symfony\Component\DependencyInjection\Definition;
$definition = new Definition(
'AppBundle\Client\ClientConfiguration',
array()
);
$definition->setScope('client');
$definition->setSynchronized(true);
$definition->setSynthetic(true);
$container->setDefinition('client_configuration', $definition);
Now, if you inject this service using setter injection, there are no drawbacks
and everything works without any special code in your service or in your definition::

// src/AppBundle/Mail/Mailer.php
namespace AppBundle\Mail;

use AppBundle\Client\ClientConfiguration;

class Mailer
{
protected $clientConfiguration;

public function setClientConfiguration(ClientConfiguration $clientConfiguration = null)
{
$this->clientConfiguration = $clientConfiguration;
}

public function sendEmail()
{
if (null === $this->clientConfiguration) {
// throw an error?
}

// ... do something using the client configuration here
}
}

Whenever the ``client`` scope is active, the service container will
automatically call the ``setClientConfiguration()`` method when the
``client_configuration`` service is set in the container.

You might have noticed that the ``setClientConfiguration()`` method accepts
``null`` as a valid value for the ``client_configuration`` argument. That's
because when leaving the ``client`` scope, the ``client_configuration`` instance
can be ``null``. Of course, you should take care of this possibility in
your code. This should also be taken into account when declaring your service:

.. configuration-block::

.. code-block:: yaml
# app/config/services.yml
services:
my_mailer:
class: AppBundle\Mail\Mailer
calls:
- [setClientConfiguration, ["@?client_configuration="]]
.. code-block:: xml
<!-- app/config/services.xml -->
<services>
<service id="my_mailer"
class="AppBundle\Mail\Mailer"
>
<call method="setClientConfiguration">
<argument
type="service"
id="client_configuration"
on-invalid="null"
strict="false"
/>
</call>
</service>
</services>
.. code-block:: php
// app/config/services.php
use Symfony\Component\DependencyInjection\Definition;
use Symfony\Component\DependencyInjection\ContainerInterface;
.. note::

$definition = $container->setDefinition(
'my_mailer',
new Definition('AppBundle\Mail\Mailer')
)
->addMethodCall('setClientConfiguration', array(
new Reference(
'client_configuration',
ContainerInterface::NULL_ON_INVALID_REFERENCE,
false
)
));
In Symfony 2.6 and previous versions, there was another alternative based
on ``synchronized`` services. However, these kind of services have been
removed starting from Symfony 2.7.

.. _changing-service-scope:

B) Changing the Scope of your Service
A) Changing the Scope of your Service
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Changing the scope of a service should be done in its definition. This example
Expand Down Expand Up @@ -302,7 +162,7 @@ argument is the ``ClientConfiguration`` object:
.. _passing-container:

C) Passing the Container as a Dependency of your Service
B) Passing the Container as a Dependency of your Service
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Setting the scope to a narrower one is not always possible (for instance, a
Expand Down Expand Up @@ -338,7 +198,7 @@ into your service::
in the first section (except that Symfony cannot detect that you are
wrong).

The service config for this class would look something like this:
The service configuration for this class would look something like this:

.. configuration-block::

Expand Down

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