add the generic handler and the request classes

Trismegiste · Trismegiste · commit 5ef810f3d0e9 · 2013-05-12T20:52:29.000+02:00
diff --git a/ChainOfResponsibilities/Handler.php b/ChainOfResponsibilities/Handler.php
@@ -0,0 +1,58 @@
+<?php
+
+/*
+ * DesignPatternPHP
+ */
+
+namespace DesignPatterns\ChainOfResponsibilities;
+
+/**
+ * Handler is a generic handler in the chain of responsibilities
+ */
+abstract class Handler implements KeyValueStorage
+{
+
+    protected $successor = null;
+
+    /**
+     * Append a responsibility to the end of chain
+     * 
+     * A prepend method could be done with the same spirit
+     * 
+     * You could also send the successor in the contructor but in PHP it is a
+     * bad idea because you have to remove the type-hint of the parameter because
+     * the last handler has a null successor.
+     * 
+     * And if you override the contructor, your Handler can no longer have a
+     * successor. One solution is to provide a NullObject (see pattern) 
+     */
+    final public function append(Handler $handler)
+    {
+        if (is_null($this->successor)) {
+            $this->successor = $handler;
+        } else {
+            $this->successor->append($handler);
+        }
+    }
+
+    /**
+     * Handle the request. 
+     * 
+     * This approach by using a template method pattern ensures you that 
+     * each subclass will not forget to call the successor. Beside, the returned
+     * boolean value indicates you if the request have been processed or not.
+     */
+    final public function handle(Request $req)
+    {
+        $processed = $this->processing($req);
+        if (!$processed) {
+            if (!is_null($this->successor)) {
+                $processed = $this->successor->handle($req);
+            }
+        }
+
+        return $processed;
+    }
+
+    abstract protected function processing(Request $req);
+}
diff --git a/ChainOfResponsibilities/Request.php b/ChainOfResponsibilities/Request.php
@@ -0,0 +1,23 @@
+<?php
+
+/*
+ * DesignPatternPHP
+ */
+
+namespace DesignPatterns\ChainOfResponsibilities;
+
+/**
+ * Request is a request which goes throught the chain of responsibilities.
+ * 
+ * About the request : Sometimes, you don't need an object, just an integer or
+ * an array. But in this case of a full example, I've made a class to illustrate 
+ * this important idea in the CoR (Chain of Responsibilities). In real world,
+ * I recommand to always use a class, even a \stdClass if you want, it proves
+ * to be more adaptative because a single handler doesn't know much about the
+ * outside world and it is more difficult if, one day, you want add some 
+ * criterion in a decision process. 
+ */
+class Request
+{
+    
+}
diff --git a/Tests/ChainOfResponsibilities/ChainTest.php b/Tests/ChainOfResponsibilities/ChainTest.php
@@ -0,0 +1,22 @@
+<?php
+
+/*
+ * DesignPatternPHP
+ */
+
+namespace DesignPatterns\Tests\ChainOfResponsibilities;
+
+use DesignPatterns\ChainOfResponsibilities\Request;
+
+/**
+ * ChainTest tests the CoR
+ */
+class ChainTest extends \PHPUnit_Framework_TestCase
+{
+
+    public function testProcess()
+    {
+        
+    }
+
+}
