added a way to set requirements on the routes

$app->get('/{id}', function($id) {
    // ...
})->assert('id', '\d+');

src/Silex/Controller.php

@@ -64,6 +64,21 @@ class Controller
         }
 
         $this->routeName = $routeName;
+
+        return $this;
+    }
+
+    /**
+     * Sets the requirement for a route variable.
+     *
+     * @param string $variable The variable name
+     * @param string $regexp   The regexp to apply
+     */
+    public function assert($variable, $regexp)
+    {
+        $this->route->setRequirement($variable, $regexp);
+
+        return $this;
     }
 
     /**

tests/Silex/Tests/ControllerTest.php

@@ -24,7 +24,9 @@ class ControllerTest extends \PHPUnit_Framework_TestCase
     public function testBind()
     {
         $controller = new Controller(new Route('/foo'));
-        $controller->bind('foo');
+        $ret = $controller->bind('foo');
+
+        $this->assertSame($ret, $controller);
         $this->assertEquals('foo', $controller->getRouteName());
     }
 
@@ -38,4 +40,13 @@ class ControllerTest extends \PHPUnit_Framework_TestCase
         $controller->freeze();
         $controller->bind('bar');
     }
+
+    public function testAssert()
+    {
+        $controller = new Controller(new Route('/foo/{bar}'));
+        $ret = $controller->assert('bar', '\d+');
+
+        $this->assertSame($ret, $controller);
+        $this->assertEquals(array('bar' => '\d+'), $controller->getRoute()->getRequirements());
+    }
 }