fixed documentation (closes #375)

doc/providers/security.rst

@@ -127,14 +127,22 @@ Each user is defined with the following information:
 
 The default configuration of the extension enforces encoded passwords. To
 generate a valid encoded password from a raw password, use the
-``security.encoder`` service::
+``security.encoder_factory`` service::
 
-    // find the encoded password for foo
-    $password = $app['security.encoder']->encodePassword('foo', null);
+    // find the encoder for the User class (which is the default)
+    $encoder = $app['security.encoder_factory']->getEncoder('Symfony\Component\Security\Core\User\User');
+
+    // compute the encoded password for foo
+    $password = $encoder->encodePassword('foo', null);
 
 The second argument is the salt to be used for the user (defaults to
 ``null``).
 
+You can also get the encoder directly by its name. By default, use the
+``security.encoder.digest`` service::
+
+    $password = $app['security.encoder.digest']->encodePassword('foo', null);
+
 When the user is authenticated, the user stored in the token is an instance of
 `User
 <http://api.symfony.com/master/Symfony/Component/Security/Core/User/User.html>`_