--- /dev/null
+<?php
+
+/*
+ * This file is part of the Symfony CMF package.
+ *
+ * (c) 2011-2015 Symfony CMF
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Cmf\Component\Routing\Enhancer;
+
+use Symfony\Component\HttpFoundation\Request;
+
+/**
+ * This enhancer sets a field to a fixed value. You can specify a source field
+ * name to only set the target field if the source is present.
+ *
+ * @author David Buchmann
+ */
+class FieldPresenceEnhancer implements RouteEnhancerInterface
+{
+ /**
+ * Field name for the source field that must exist. If null, the target
+ * field is always set if not already present.
+ *
+ * @var string|null
+ */
+ protected $source;
+
+ /**
+ * Field name to write the value into.
+ *
+ * @var string
+ */
+ protected $target;
+
+ /**
+ * Value to set the target field to.
+ *
+ * @var string
+ */
+ private $value;
+
+ /**
+ * @param null|string $source the field name of the class, null to disable the check
+ * @param string $target the field name to set from the map
+ * @param string $value value to set target field to if source field exists
+ */
+ public function __construct($source, $target, $value)
+ {
+ $this->source = $source;
+ $this->target = $target;
+ $this->value = $value;
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function enhance(array $defaults, Request $request)
+ {
+ if (isset($defaults[$this->target])) {
+ // no need to do anything
+ return $defaults;
+ }
+
+ if (null !== $this->source && !isset($defaults[$this->source])) {
+ return $defaults;
+ }
+
+ $defaults[$this->target] = $this->value;
+
+ return $defaults;
+ }
+}