[#4228] Move synthetic services to its own recipe

Author: wouterj

components/dependency_injection/advanced.rst

@@ -73,61 +73,6 @@ below) to access this service (via the alias).
 
    Services are by default public.
 
-Synthetic Services
-------------------
-
-Synthetic services are services that are injected into the container instead
-of being created by the container.
-
-For example, if you're using the :doc:`HttpKernel </components/http_kernel/introduction>`
-component with the DependencyInjection component, then the ``request``
-service is injected in the
-:method:`ContainerAwareHttpKernel::handle() <Symfony\\Component\\HttpKernel\\DependencyInjection\\ContainerAwareHttpKernel::handle>`
-method when entering the request :doc:`scope </cookbook/service_container/scopes>`.
-The class does not exist when there is no request, so it can't be included in
-the container configuration. Also, the service should be different for every
-subrequest in the application.
-
-To create a synthetic service, set ``synthetic`` to ``true``:
-
-.. configuration-block::
-
-    .. code-block:: yaml
-
-        services:
-            request:
-                synthetic: true
-
-    .. code-block:: 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="request" synthetic="true" />
-            </services>
-        </container>
-
-    .. code-block:: php
-
-        use Symfony\Component\DependencyInjection\Definition;
-
-        $container
-            ->setDefinition('request', new Definition())
-            ->setSynthetic(true);
-
-As you see, only the ``synthetic`` option is set. All other options are only used
-to configure how a service is created by the container. As the service isn't
-created by the container, these options are omitted.
-
-Now, you can inject the class by using
-:method:`Container::set <Symfony\\Component\\DependencyInjection\\Container::set>`::
-
-    // ...
-    $container->set('request', new MyRequest(...));
-
 Aliasing
 --------
 

components/dependency_injection/index.rst

@@ -8,6 +8,7 @@
     types
     parameters
     definitions
+    synthetic_services
     compilation
     tags
     factories

components/dependency_injection/synthetic_services.rst

@@ -0,0 +1,50 @@
+.. index::
+    single: DependencyInjection; Synthetic Services
+
+How to Inject Instances into the Container
+------------------------------------------
+
+When using the container in your application, you sometimes need to inject an
+instance instead of configuring the container to create a new instance.
+
+For instance, if you're using the :doc:`HttpKernel </components/http_kernel/introduction>`
+component with the DependencyInjection component, then the ``kernel``
+service is injected into the container from within the ``Kernel`` class::
+
+    // ...
+    abstract class Kernel implements KernelInterface, TerminableInterface
+    {
+        // ...
+        protected function initializeContainer()
+        {
+            // ...
+            $this->container->set('kernel', $this);
+
+            // ...
+        }
+    }
+
+The ``kernel`` service is called a synthetic service. This service has to be
+configured in the container, so the container knows the service does exist
+during compilation (otherwise, services depending on this ``kernel`` service
+will get a "service does not exists" error).
+
+In order to do so, you have to use
+:method:`Definition::setSynthetic() <Symfony\\Component\\DependencyInjection\\Definition::setSynthetic>`::
+
+    use Symfony\Component\DependencyInjectino\Definition;
+
+    // synthetic services don't specify a class
+    $kernelDefinition = new Definition();
+    $kernelDefinition->setSynthetic(true);
+
+    $container->setDefinition('your_service', $kernelDefinition);
+
+Now, you can inject the instance in the container using
+:method:`Container::set() <Symfony\\Component\\DependencyInjection\\Container::set>`::
+
+    $yourService = new YourObject();
+    $container->set('your_service', $yourService);
+
+``$container->get('your_service')`` will now return the same instance as
+``$yourService``.

components/map.rst.inc

@@ -39,6 +39,7 @@
   * :doc:`/components/dependency_injection/types`
   * :doc:`/components/dependency_injection/parameters`
   * :doc:`/components/dependency_injection/definitions`
+  * :doc:`/components/dependency_injection/synthetic_services`
   * :doc:`/components/dependency_injection/compilation`
   * :doc:`/components/dependency_injection/tags`
   * :doc:`/components/dependency_injection/factories`