use short config syntax for factories

Author: Henry Snoek

service_container/factories.rst

@@ -52,7 +52,7 @@ configure the service container to use the
             app.newsletter_manager:
                 class:   AppBundle\Email\NewsletterManager
                 # call a method on the specified service
-                factory: ['@app.newsletter_manager_factory', createNewsletterManager]
+                factory: 'app.newsletter_manager_factory:createNewsletterManager'
 
     .. code-block:: xml
 
@@ -111,6 +111,19 @@ configure the service container to use the
     the configured class name may be used by compiler passes and therefore
     should be set to a sensible value.
 
+.. note::
+
+    The traditional configuration syntax in YAML files used an array to define
+    the factory service and the method name:
+
+    .. code-block:: yaml
+
+        app.newsletter_manager:
+            # new syntax
+            factory: 'app.newsletter_manager_factory:createNewsletterManager'
+            # old syntax
+            factory: ['@app.newsletter_manager_factory', createNewsletterManager]
+
 Passing Arguments to the Factory Method
 ---------------------------------------
 
@@ -127,7 +140,7 @@ method in the previous example takes the ``templating`` service as an argument:
 
             app.newsletter_manager:
                 class:     AppBundle\Email\NewsletterManager
-                factory:   ['@newsletter_manager_factory', createNewsletterManager]
+                factory:   'newsletter_manager_factory:createNewsletterManager'
                 arguments: ['@templating']
 
     .. code-block:: xml