Added key parameter to filter strategy callback.

Updated documentation for filter strategy.

Author: Paul

README.md

@@ -518,7 +518,7 @@ Filter(Strategy|Mapping|array|mixed $expression, callable $callback = null)
 ```
 
  1. `$expression` – Expression.
- 2. `$callback` – Callback function that receives the current value as its first argument.
+ 2. `$callback` – Callback function that receives the current value as its first argument, the current key as its second argument and context as its third argument.
 
 #### Example
 

src/Strategy/Filter.php

@@ -4,15 +4,19 @@
 use ScriptFUSION\Mapper\Mapping;
 
 /**
- * Filters null values or values rejected by the specified callback
+ * Filters null values or values rejected by the specified callback.
  */
 class Filter extends Delegate
 {
+    /**
+     * @var callable|null
+     */
     private $callback;
 
     /**
      * @param Strategy|Mapping|array|mixed $expression Expression.
-     * @param callable|null $callback Callback function that receives the current value as its first argument.
+     * @param callable|null $callback Callback function that receives the current value as its first argument, the
+     *     current key as its second argument and context as its third argument.
      */
     public function __construct($expression, callable $callback = null)
     {
@@ -27,18 +31,20 @@ public function __invoke($data, $context = null)
             return null;
         }
 
-        $filter = function (array $data, $context) {
-            $callback = $this->callback ?: function ($value) {
-                return $value !== null;
-            };
+        return iterator_to_array(self::filter($this->callback ?: [$this, 'filterNulls'], $data, $context));
+    }
 
-            foreach ($data as $datum) {
-                if ($callback($datum, $context)) {
-                    yield $datum;
-                }
+    private static function filter(callable $callback, array $data, $context)
+    {
+        foreach ($data as $key => $datum) {
+            if ($callback($datum, $key, $context)) {
+                yield $key => $datum;
             }
-        };
+        }
+    }
 
-        return iterator_to_array($filter($data, $context));
+    private static function filterNulls($value)
+    {
+        return $value !== null;
     }
 }

test/Unit/Mapper/Strategy/FilterTest.php

@@ -12,32 +12,38 @@ final class FilterTest extends \PHPUnit_Framework_TestCase
     public function testDefaultCallback()
     {
         $filter = new Filter(null);
-        $filter->setMapper(MockFactory::mockMapper([null, 0, "0", null]));
+        $filter->setMapper(MockFactory::mockMapper([null, 0, '0', null]));
 
-        self::assertEquals([0, "0"], array_values($filter([])));
+        self::assertSame([1 => 0, 2 => '0'], $filter([]));
     }
 
-    public function testCustomCallback()
+    public function testFilterByValue()
     {
         $filter = new Filter(null, function ($value) {
             return $value['foo'] === 'bar';
         });
 
         $filter->setMapper(MockFactory::mockMapper([
-            [
-                'foo' => 'bar',
-            ],
-            [
-                'foo' => 'baz',
-            ],
+            $bar = ['foo' => 'bar'],
+            ['foo' => 'baz'],
         ]));
 
-        self::assertEquals([['foo' => 'bar']], $filter([]));
+        self::assertSame([$bar], $filter([]));
+    }
+
+    public function testFilterByKey()
+    {
+        $filter = new Filter(null, function ($_, $key) {
+            return $key % 2;
+        });
+        $filter->setMapper(MockFactory::mockMapper(range('a', 'e')));
+
+        self::assertSame([1 => 'b', 3 => 'd'], $filter([]));
     }
 
     public function testContextPassed()
     {
-        $filter = new Filter(null, function ($_, $context) {
+        $filter = new Filter(null, function ($_, $__, $context) {
             self::assertSame('foo', $context);
         });
         $filter->setMapper(MockFactory::mockMapper(['bar']));