a relevant example for iterator

Iterator/CardGame.php

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+<?php
+
+/*
+ * DesignPatternPHP
+ */
+
+namespace DesignPatterns\Iterator;
+
+/**
+ * Iterator provides a standard way to iterate over a collection without knowing
+ * how it is implemented. All you need to know is : you can traverse it
+ * with current, valid, next, rewind and key.
+ * 
+ * That's the key feature of this pattern :
+ * The underlaying machinery could be an array, a matrix, a file, a cursor
+ * from database, a webservice with a cache, you don't care anymore.
+ * 
+ * Note: This design pattern changes from one language to another. It depends 
+ * mostly how loop statements handle collections (see Java before and after 1.5)
+ * 
+ * In this simple example, I try to demonstrate how I manage a "linear" iterator
+ * on a card game but in fact, the underlaying storage is handled by two combined
+ * arrays.
+ * 
+ * If tomorrow you decide to read cards from a database, the client 
+ * (see the PHPUnit test) will remain unchanged. That's beauty of it.
+ */
+class CardGame implements \Iterator
+{
+
+    protected $color = array('D', 'S', 'C', 'H');
+    protected $number = array(7, 8, 9, 10, 'J', 'Q', 'K', 'A');
+
+    /**
+     * Return the current value
+     */
+    public function current()
+    {
+        return current($this->number) . ' of ' . current($this->color);
+    }
+
+    /**
+     * Return the current key
+     */
+    public function key()
+    {
+        return current($this->color) . current($this->number);
+    }
+
+    /**
+     * Go to the next item in the collection
+     */
+    public function next()
+    {
+        if (false === next($this->number)) {
+            if (false !== next($this->color)) {
+                reset($this->number);
+            }
+        }
+    }
+
+    /**
+     * Go to the first item in the collection
+     */
+    public function rewind()
+    {
+        reset($this->color);
+        reset($this->number);
+    }
+
+    /**
+     * Is the current position a valid item (true) 
+     * or do we reach the end (false) ?
+     */
+    public function valid()
+    {
+        return current($this->number) || current($this->color);
+    }
+
+}

Tests/Iterator/IteratorTest.php

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+<?php
+
+/*
+ * DesignPatternPHP
+ */
+
+namespace DesignPatterns\Tests\Iterator;
+
+use DesignPatterns\Iterator\CardGame;
+
+/**
+ * IteratorTest the CardGame iterator
+ *
+ * @author flo
+ */
+class IteratorTest extends \PHPUnit_Framework_TestCase
+{
+
+    protected $game;
+
+    protected function setUp()
+    {
+        $this->game = new CardGame();
+    }
+
+    /**
+     * This is the client of the iterator.
+     * It remains unchanged even if one I decide to use MongoDB to store the
+     * card.
+     */
+    public function testCardinal()
+    {
+        $counter = 0;
+        foreach ($this->game as $key => $card) {
+            $counter++;
+        }
+
+        $this->assertEquals(32, $counter);
+    }
+
+    /**
+     * Some fancy functions of PHP.
+     */
+    public function testExampleOf_PHP_Helper()
+    {
+        // PHPUnit works on array or iterator :
+        $this->assertCount(32, $this->game);
+        // a easy way to get an array from interator :
+        $cards = iterator_to_array($this->game);
+        $this->assertEquals('A of S', $cards['SA']);
+        // a easy way to get an iterator from an array :
+        $iterator = new \ArrayIterator($cards);
+        $this->assertInstanceOf('\Iterator', $iterator);
+    }
+
+}