MINOR Documented and unit tested ArrayLib::invert() (merged from branches/2.3-nzct)

git-svn-id: svn://svn.silverstripe.com/silverstripe/open/modules/sapphire/trunk@82068 467b73ca-7a2a-4603-9d3b-597d59a354a9

core/ArrayLib.php

@@ -5,15 +5,54 @@
  * @subpackage misc
  */
 class ArrayLib extends Object {
+	
+	/**
+	 * Inverses the first and second level keys of an associative
+	 * array, keying the result by the second level, and combines
+	 * all first level entries within them.
+	 * 
+	 * Before:
+	 * <example>
+	 * array(
+	 * 	'row1' => array(
+	 * 		'col1' =>'val1',
+	 * 		'col2' => 'val2'
+	 * 	),
+	 * 	'row2' => array(
+	 * 		'col1' => 'val3',
+	 * 		'col2' => 'val4'
+	 * 	)
+	 * )
+	 * </example>
+	 * 
+	 * After:
+	 * <example>
+	 * array(
+	 * 	'col1' => array(
+	 * 		'row1' => 'val1',
+	 * 		'row2' => 'val3',
+	 * 	),
+	 * 	'col2' => array(
+	 * 		'row1' => 'val2',
+	 * 		'row2' => 'val4',
+	 * 	),
+	 * )
+	 * </example>
+	 * 
+	 * @param array $arr
+	 * @return array
+	 */
 	static function invert($arr) {
-		if (! $arr) return false;
+		if(!$arr) return false;
+		$result = array();
 		
 		foreach($arr as $columnName => $column) {
 			foreach($column as $rowName => $cell) {
-				$output[$rowName][$columnName] = $cell;
+				$result[$rowName][$columnName] = $cell;
 			}
 		}
-		return $output;
+		
+		return $result;
 	}
 	
 	/**

tests/ArrayLibTest.php

@@ -0,0 +1,33 @@
+<?php
+/**
+ * @package sapphire
+ * @subpackage tests
+ */
+class ArrayLibTest extends SapphireTest {
+	function testInvert() {
+		$arr = array(
+			'row1' => array(
+				'col1' =>'val1',
+				'col2' => 'val2'
+			),
+			'row2' => array(
+				'col1' => 'val3',
+				'col2' => 'val4'
+			)
+		);
+		
+		$this->assertEquals(
+			ArrayLib::invert($arr),
+			array(
+				'col1' => array(
+					'row1' => 'val1',
+					'row2' => 'val3',
+				),
+				'col2' => array(
+					'row1' => 'val2',
+					'row2' => 'val4',
+				),
+			)
+		);
+	}
+}