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lib/pkp/classes/core/traits/EntityWithParent.php

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+<?php
+
+/**
+ * @file classes/core/traits/EntityWithParent.php
+ *
+ * Copyright (c) 2022 Simon Fraser University
+ * Copyright (c) 2022 John Willinsky
+ * Distributed under the GNU GPL v3. For full terms see the file docs/COPYING.
+ *
+ * @class EntityWithParent
+ *
+ * @ingroup core_traits
+ *
+ * @brief A trait for DAO classes that can be used with entities that have a parent entity. For example, a Submission always has a parent Context.
+ *
+ */
+
+namespace PKP\core\traits;
+
+use Illuminate\Database\Query\Builder;
+use Illuminate\Support\Facades\DB;
+use PKP\core\DataObject;
+
+/**
+ * @template T of DataObject
+ */
+trait EntityWithParent
+{
+    /**
+     * Get the parent object ID column name
+     */
+    abstract public function getParentColumn(): string;
+
+    /**
+     * @copydoc EntityDAO::fromRow()
+     *
+     * @return T
+     */
+    abstract public function fromRow(object $row): DataObject;
+
+    /**
+     * Check if an object exists.
+     *
+     * Optionally, pass the ID of a parent entity to check if the object
+     * exists and is assigned to that parent.
+     */
+    public function exists(int $id, int $parentId = null): bool
+    {
+        return DB::table($this->table)
+            ->where($this->primaryKeyColumn, '=', $id)
+            ->when($parentId !== null, fn (Builder $query) => $query->where($this->getParentColumn(), $parentId))
+            ->exists();
+    }
+
+    /**
+     * Get an object.
+     *
+     * Optionally, pass the ID of a parent entity to only get an object
+     * if it exists and is assigned to that parent.
+     *
+     * @return ?T
+     */
+    public function get(int $id, int $parentId = null): ?DataObject
+    {
+        $row = DB::table($this->table)
+            ->where($this->primaryKeyColumn, $id)
+            ->when($parentId !== null, fn (Builder $query) => $query->where($this->getParentColumn(), $parentId))
+            ->first();
+        return $row ? $this->fromRow($row) : null;
+    }
+}