refactor!: Make Collection an instantiable class.

src/Domain/Collection.php

@@ -10,18 +10,22 @@
 use IteratorAggregate;
 use Traversable;
 
-abstract class Collection implements Countable, IteratorAggregate
+class Collection implements Countable, IteratorAggregate
 {
     /**
      * @template T of object
      * @extends IteratorAggregate<T>
      *
      * @param T[] $items
+     * @param class-string<T> $itemType
      */
     final public function __construct(
         private readonly array $items = [],
+        ?string $itemType = null,
     ) {
-        Assert\Assertion::allIsInstanceOf($items, $this->itemType());
+        if ($itemType !== null) {
+            Assert\Assertion::allIsInstanceOf($items, $itemType);
+        }
     }
 
     /**
@@ -39,16 +43,4 @@ public function count(): int
     {
         return count($this->items);
     }
-
-    /**
-     * @inheritDoc
-     */
-
-    /**
-     * Return the type of the items in the collection.
-     * This is a poor man's workaround for missing generics in PHP.
-     *
-     * @return string
-     */
-    abstract protected function itemType(): string;
 }

src/Infrastructure/InMemory/Repository.php

@@ -23,23 +23,19 @@ abstract class Repository implements RepositoryInterface
      * @extends IteratorAggregate<T>
      *
      * @param class-string<T> $itemType
-     * @param class-string<Collection<T>> $collectionType
      */
     public function __construct(
         private string $itemType,
-        private string $collectionType,
     ) {
         Assert::that($this->itemType)->classExists();
-        Assert::that($this->collectionType)->classExists();
     }
 
     /**
      * @inheritDoc
      */
     public function collect(): Collection
     {
-        $collectionClass = $this->collectionType;
-        return new $collectionClass($this->items);
+        return new Collection($this->items, $this->itemType);
     }
 
     /**

tests/Domain/CollectionTest.php

@@ -17,33 +17,20 @@ class Foo
 {
 }
 
-/**
- * Test subject.
- *
- * @package GeekCell\Ddd\Tests\Domain
- */
-class TestCollection extends Collection
-{
-    protected function itemType(): string
-    {
-        return Foo::class;
-    }
-}
-
 class CollectionTest extends TestCase
 {
-    public function testConstructor(): void
+    public function testTypedConstructor(): void
     {
         // Given
         $items = [new Foo(), new Foo(), new Foo()];
 
         // When
-        $collection = new TestCollection($items);
+        $collection = new Collection($items, Foo::class);
 
-        $this->assertInstanceOf(TestCollection::class, $collection);
+        $this->assertInstanceOf(Collection::class, $collection);
     }
 
-    public function testConstructorWithInvalidType(): void
+    public function testTypedConstructorWithInvalidType(): void
     {
         // Given
         $items = [new Foo(), new Foo(), new \stdClass()];
@@ -52,7 +39,18 @@ public function testConstructorWithInvalidType(): void
         $this->expectException(Assert\InvalidArgumentException::class);
 
         // When
-        $collection = new TestCollection($items);
+        $collection = new Collection($items, Foo::class);
+    }
+
+    public function testUntypedConstructor(): void
+    {
+        // Given
+        $items = [new Foo(), new \stdClass(), 42, 'foo'];
+
+        // When
+        $collection = new Collection($items);
+
+        $this->assertInstanceOf(Collection::class, $collection);
     }
 
     public function testCount(): void
@@ -61,7 +59,7 @@ public function testCount(): void
         $items = [new Foo(), new Foo(), new Foo()];
 
         // When
-        $collection = new TestCollection($items);
+        $collection = new Collection($items, Foo::class);
 
         // Then
         $this->assertCount(3, $collection);
@@ -73,7 +71,7 @@ public function testIterater(): void
         $items = [new Foo(), new Foo(), new Foo()];
 
         // When
-        $collection = new TestCollection($items);
+        $collection = new Collection($items, Foo::class);
 
         // Then
         $this->assertEquals($items, iterator_to_array($collection));

tests/Infrastructure/InMemory/RepositoryTest.php

@@ -11,19 +11,6 @@
 use GeekCell\Ddd\Tests\Fixtures\Counter;
 use PHPUnit\Framework\TestCase;
 
-/**
- * Test fixture for InMemoryRepository.
- *
- * @package GeekCell\Ddd\Tests\Infrastructure
- */
-class CounterCollection extends Collection
-{
-    protected function itemType(): string
-    {
-        return Counter::class;
-    }
-}
-
 /**
  * Test subject.
  *
@@ -33,10 +20,7 @@ class InMemoryTestRepository extends InMemoryRepository
 {
     public function __construct()
     {
-        parent::__construct(
-            Counter::class,
-            CounterCollection::class
-        );
+        parent::__construct(Counter::class);
     }
 
     public function setItems(array $items): void
@@ -74,10 +58,7 @@ public function testConstructWithInvalidTypes(): void
         $instance = new class () extends InMemoryRepository {
             public function __construct()
             {
-                parent::__construct(
-                    'Foo\Bar\Baz',
-                    'Foo\Bar\BazCollection'
-                );
+                parent::__construct('Foo\Bar\Baz');
             }
         };
     }
@@ -96,7 +77,7 @@ public function testCollectAndCount(): void
         $result = $repository->collect();
 
         // Then
-        $this->assertInstanceOf(CounterCollection::class, $result);
+        $this->assertInstanceOf(Collection::class, $result);
         $this->assertEquals(count($this->items), count($result));
     }