full visitor pattern withh double dispatch

Visitor/Role.php

@@ -0,0 +1,38 @@
+<?php
+
+namespace DesignPatterns\Visitor;
+
+/**
+ * Visitor Pattern
+ *
+ * Purpose:
+ * The Visitor Pattern lets you outsource operations on objects to other objects. The main reason to do this is to keep
+ * a seperation of concerns. But classes have to define an contract to allow visitors (the "accept" method in the example below).
+ * 
+ * The contract is an abstract class but you can have also a clean interface
+ */
+abstract class Role
+{
+
+    /**
+     * This method handle a double dispatch based on the shortname of the Visitee
+     * 
+     * Feel free to override it if your object must call another visiting behavior
+     * 
+     * @param \DesignPatterns\Visitor\RoleVisitor $visitor
+     */
+    public function accept(RoleVisitor $visitor)
+    {
+        // this trick to simulate double-dispatch based on type-hinting
+        $fqcn = get_called_class();
+        preg_match('#([^\\\\]+)$#', $fqcn, $extract);
+        $visitingMethod = 'visit' . $extract[1];
+
+        if (!method_exists($visitor, $visitingMethod)) {
+            throw new \InvalidArgumentException("The visitor you provide cannot visit a $fqcn object");
+        }
+
+        call_user_func(array($visitor, $visitingMethod), $this);
+    }
+
+}