[Feat] Map Array to Single Element Key Value (#161)

* feat: map array to single element key value

* refactor: param callback return as array with type

Author: SonyPradana

src/System/Collection/Collection.php

@@ -365,4 +365,28 @@ public function shuffle(): self
 
         return $this->replace($reordered);
     }
+
+    /**
+     * Convert array, key and value from item (also key).
+     *
+     * @template TKeyItem of array-key
+     * @template TValueItem
+     *
+     * @param callable(TValue, TKey=): array<TKeyItem, TValueItem> $callable With single key/value pair per element
+     *
+     * @return $this
+     */
+    public function assocBy(callable $callable): self
+    {
+        /** @var array<TKeyItem, TValueItem> */
+        $new_collection = [];
+        foreach ($this->collection as $key => $item) {
+            $array_assoc = call_user_func($callable, $item, $key);
+            if (array_key_exists(0, $array_assoc) && array_key_exists(1, $array_assoc)) {
+                $new_collection[$array_assoc[0]] = $array_assoc[1];
+            }
+        }
+
+        return $this->replace($new_collection);
+    }
 }

tests/Collection/CollectionTest.php

@@ -356,6 +356,27 @@ public function itCanByShuffle()
         }
     }
 
+    /** @test */
+    public function itCanMapWithKeys()
+    {
+        $arr = new Collection([
+            [
+                'name'  => 'taylor',
+                'email' => 'taylor@laravel.com',
+            ], [
+                'name'  => 'pradana',
+                'email' => 'pradana@savanna.com',
+            ],
+        ]);
+
+        $assocBy = $arr->assocBy(fn ($item) => [$item['name'], $item['email']]);
+
+        $this->assertEquals([
+            'taylor'  => 'taylor@laravel.com',
+            'pradana' => 'pradana@savanna.com',
+        ], $assocBy->toArray());
+    }
+
     /** @test */
     public function itCanCloneColection()
     {