full visitor pattern withh double dispatch

Tests/Visitor/VisitorTest.php

@@ -0,0 +1,51 @@
+<?php
+
+/*
+ * DesignPatternPHP
+ */
+
+namespace DesignPatterns\Tests\Visitor;
+
+use DesignPatterns\Visitor;
+
+/**
+ * VisitorTest tests the visitor pattern
+ */
+class VisitorTest extends \PHPUnit_Framework_TestCase
+{
+
+    protected $visitor;
+
+    protected function setUp()
+    {
+        $this->visitor = new Visitor\RolePrintVisitor();
+    }
+
+    public function getRole()
+    {
+        return array(
+            array(new Visitor\User("Dominik"), 'Role: User Dominik'),
+            array(new Visitor\Group("Administrators"), 'Role: Group: Administrators')
+        );
+    }
+
+    /**
+     * @dataProvider getRole
+     */
+    public function testVisitSomeRole(Visitor\Role $role, $expect)
+    {
+        $this->expectOutputString($expect);
+        $role->accept($this->visitor);
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     * @expectedExceptionMessage Mock
+     */
+    public function testUnknownObject()
+    {
+        $mock = $this->getMockForAbstractClass('DesignPatterns\Visitor\Role');
+        $mock->accept($this->visitor);
+    }
+
+}

Visitor/Group.php

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+<?php
+
+namespace DesignPatterns\Visitor;
+
+/**
+ * An example of a Visitee : Group
+ */
+class Group extends Role
+{
+
+    /**
+     * @var string
+     */
+    protected $name;
+
+    /**
+     * @param string $name
+     */
+    public function __construct($name)
+    {
+        $this->name = (string) $name;
+    }
+
+    /**
+     * @return string
+     */
+    public function getName()
+    {
+        return "Group: " . $this->name;
+    }
+
+}

Visitor/Role.php

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+<?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);
+    }
+
+}

Visitor/RolePrintVisitor.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace DesignPatterns\Visitor;
+
+/**
+ * Visitor Pattern
+ *
+ * An implementation of a Visitor
+ */
+class RolePrintVisitor implements RoleVisitor
+{
+
+    public function visitGroup(Group $role)
+    {
+        echo "Role: " . $role->getName();
+    }
+
+    public function visitUser(User $role)
+    {
+        echo "Role: " . $role->getName();
+    }
+
+}

Visitor/RoleVisitor.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace DesignPatterns\Visitor;
+
+/**
+ * Visitor Pattern
+ *
+ * The contract for the visitor
+ */
+interface RoleVisitor
+{
+
+    /**
+     * Visit a user object
+     * 
+     * @param \DesignPatterns\Visitor\User $role
+     */
+    public function visitUser(User $role);
+
+    /**
+     * Visit a Group objet
+     * 
+     * @param \DesignPatterns\Visitor\Group $role
+     */
+    public function visitGroup(Group $role);
+}

Visitor/User.php

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+<?php
+
+namespace DesignPatterns\Visitor;
+
+/**
+ * Visitor Pattern
+ *
+ * One example for a visitee. Each visitee has to extends Role
+ */
+class User extends Role
+{
+
+    /**
+     * @var string
+     */
+    protected $name;
+
+    /**
+     * @param string $name
+     */
+    public function __construct($name)
+    {
+        $this->name = (string) $name;
+    }
+
+    /**
+     * @return string
+     */
+    public function getName()
+    {
+        return "User " . $this->name;
+    }
+
+}
+

Visitor/Visitor.php

@@ -1,97 +0,0 @@
-<?php
-
-namespace DesignPatterns;
-
-/**
- * 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 interface to allow visitors (the "accept" method in the example below).
- *
- */
-interface RoleVisitor {
-    public function visit(Role $role);
-}
-
-interface Role {
-    public function getName();
-}
-
-class RolePrintVisitor implements RoleVisitor {
-
-    /**
-     * @param Role $role
-     */
-    public function visit(Role $role) {
-        echo "Role: " . $role->getName();
-    }
-}
-
-class User implements Role {
-
-    /**
-     * @var string
-     */
-    protected $name;
-
-    /**
-     * @param string $name
-     */
-    public function __construct($name) {
-        $this->name = (string) $name;
-    }
-
-    /**
-     * @param RoleVisitor $visitor
-     * @return void
-     */
-    public function accept(RoleVisitor $visitor) {
-        $visitor->visit($this);
-    }
-
-    /**
-     * @return string
-     */
-    public function getName() {
-        return "User " . $this->name;
-    }
-}
-
-class Group implements Role {
-
-    /**
-     * @var string
-     */
-    protected $name;
-
-    /**
-     * @param string $name
-     */
-    public function __construct($name) {
-        $this->name = (string) $name;
-    }
-
-    /**
-     * @param RoleVisitor $visitor
-     * @return void
-     */
-    public function accept(RoleVisitor $visitor) {
-        $visitor->visit($this);
-    }
-
-    /**
-     * @return string
-     */
-    public function getName() {
-        return "Group: " . $this->name;
-    }
-}
-
-$user = new User("Dominik");
-$group = new Group("Administrators");
-
-$printer = new RolePrintVisitor();
-$printer->visit($user);
-$printer->visit($group);
-