Make the ResultSetDecorator implement similar methods as ResultSet.

Since the decorator is supposed to be an adapter between traversable
objects and the ORM\ResultSet class is should implement the same methods
as ResultSet. I think there is probably a separate interface that needs
to be extracted here.

Cake/ORM/ResultSetDecorator.php

@@ -17,6 +17,7 @@
 namespace Cake\ORM;
 
 use \ArrayIterator;
+use \Countable;
 use \IteratorAggregate;
 use \JsonSerializable;
 use \Serializable;
@@ -28,7 +29,7 @@
  *
  * @return void
  */
-class ResultSetDecorator implements IteratorAggregate, Serializable, JsonSerializable {
+class ResultSetDecorator implements Countable, IteratorAggregate, Serializable, JsonSerializable {
 
 	use ResultCollectionTrait;
 
@@ -39,21 +40,6 @@ class ResultSetDecorator implements IteratorAggregate, Serializable, JsonSeriali
  */
 	protected $_results;
 
-/**
- * Internal index pointer.
- *
- * @var integer
- */
-	protected $_index = 0;
-
-/**
- * The array form of the results. Used to 
- * facilitate one().
- *
- * @var array
- */
-	protected $_arrayResults;
-
 /**
  * Constructor
  *
@@ -78,18 +64,35 @@ public function getIterator() {
 /**
  * Get a single result from the results.
  *
- * @return mixed
+ * Calling this method will convert the underlying data into
+ * an array and will return the first result in the data set.
+ *
+ * @return mixed The first value in the results will be returned.
  */
 	public function one() {
-		if (empty($this->_arrayResults) && !is_array($this->_results)) {
-			$this->_arrayResults = iterator_to_array($this->_results);
+		if (!is_array($this->_results)) {
+			$this->_results = iterator_to_array($this->_results);
 		}
-		$index = $this->_index;
-		$this->_index++;
-		if (!isset($this->_arrayResults[$index])) {
+		if (count($this->_results) < 1) {
 			return false;
 		}
-		return $this->_arrayResults[$index];
+		return current($this->_results);
+	}
+
+/**
+ * Make this object countable.
+ *
+ * Part of the Countable interface. Calling this method
+ * will convert the underlying traversable object into an array and
+ * get the count of the underlying data.
+ *
+ * @return integer.
+ */
+	public function count() {
+		if (!is_array($this->_results)) {
+			$this->_results = iterator_to_array($this->_results);
+		}
+		return count($this->_results);
 	}
 
 }

Cake/Test/TestCase/ORM/ResultSetDecoratorTest.php

@@ -69,4 +69,31 @@ public function testSerialization() {
 		$serialized = serialize($decorator);
 		$this->assertEquals([1, 2, 3], unserialize($serialized)->toArray());
 	}
+
+/**
+ * Test the one() method which is part of the ResultSet duck type.
+ *
+ * @return void
+ */
+	public function testOne() {
+		$data = new \ArrayIterator([1, 2, 3]);
+		$decorator = new ResultSetDecorator($data);
+
+		$this->assertEquals(1, $decorator->one());
+		$this->assertEquals(1, $decorator->one());
+	}
+
+/**
+ * Test the count() method which is part of the ResultSet duck type.
+ *
+ * @return void
+ */
+	public function testCount() {
+		$data = new \ArrayIterator([1, 2, 3]);
+		$decorator = new ResultSetDecorator($data);
+
+		$this->assertEquals(3, $decorator->count());
+		$this->assertCount(3, $decorator);
+	}
+
 }