Rename Collection class to BaseCollection. Add BaseCollection::isValidType() method to validate type of element before add it to collection. Add BaseCollection ::prepareElements() method to allow preparation of elements in custom way.

src/Collection/BaseCollection.php

@@ -0,0 +1,81 @@
+<?php
+
+/**
+ * (c) Meritoo.pl, http://www.meritoo.pl
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Meritoo\Common\Collection;
+
+use ArrayAccess;
+use Countable;
+use IteratorAggregate;
+use Meritoo\Common\Traits\CollectionTrait;
+
+/**
+ * Collection of elements with the same type
+ *
+ * @author    Meritoo <github@meritoo.pl>
+ * @copyright Meritoo <http://www.meritoo.pl>
+ */
+abstract class BaseCollection implements Countable, ArrayAccess, IteratorAggregate
+{
+    use CollectionTrait;
+
+    /**
+     * Class constructor
+     *
+     * @param array $elements (optional) The elements of collection
+     */
+    public function __construct(array $elements = [])
+    {
+        $validated = $this->getElementsWithValidType($elements);
+        $this->elements = $this->prepareElements($validated);
+    }
+
+    /**
+     * Prepares elements to initialize the collection.
+     * Feel free to override and prepare elements in your way.
+     *
+     * @param array $elements The elements of collection to prepare
+     * @return array
+     */
+    protected function prepareElements(array $elements): array
+    {
+        return $elements;
+    }
+
+    /**
+     * Returns elements of collection with valid types
+     *
+     * @param array $elements The elements of collection to verify
+     * @return array
+     */
+    protected function getElementsWithValidType(array $elements): array
+    {
+        if (empty($elements)) {
+            return [];
+        }
+
+        $result = [];
+
+        foreach ($elements as $index => $element) {
+            if (!$this->isValidType($element)) {
+                continue;
+            }
+
+            $result[$index] = $element;
+        }
+
+        return $result;
+    }
+
+    /**
+     * Returns information if given element has valid type
+     *
+     * @param mixed $element Element of collection
+     * @return bool
+     */
+    abstract protected function isValidType($element): bool;
+}