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typo3/sysext/belog/Classes/ViewHelpers/UsernameViewHelper.php

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+<?php
+namespace TYPO3\CMS\Belog\ViewHelpers;
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+use TYPO3\CMS\Core\Utility\GeneralUtility;
+use TYPO3\CMS\Extbase\Domain\Repository\BackendUserRepository;
+use TYPO3\CMS\Extbase\Object\ObjectManager;
+use TYPO3Fluid\Fluid\Core\Rendering\RenderingContextInterface;
+use TYPO3Fluid\Fluid\Core\ViewHelper\AbstractViewHelper;
+use TYPO3Fluid\Fluid\Core\ViewHelper\Traits\CompileWithRenderStatic;
+
+/**
+ * Get username from backend user id
+ * @internal
+ */
+class UsernameViewHelper extends AbstractViewHelper
+{
+    use CompileWithRenderStatic;
+
+    /**
+     * First level cache of user names
+     *
+     * @var array
+     */
+    protected static $usernameRuntimeCache = [];
+
+    /**
+     * Initializes the arguments
+     */
+    public function initializeArguments()
+    {
+        $this->registerArgument('uid', 'int', 'Uid of the user', true);
+    }
+
+    /**
+     * Resolve user name from backend user id.
+     *
+     * @param array $arguments
+     * @param \Closure $renderChildrenClosure
+     * @param RenderingContextInterface $renderingContext
+     *
+     * @return string Username or an empty string if there is no user with that UID
+     */
+    public static function renderStatic(array $arguments, \Closure $renderChildrenClosure, RenderingContextInterface $renderingContext)
+    {
+        $uid = $arguments['uid'];
+        if (isset(static::$usernameRuntimeCache[$uid])) {
+            return static::$usernameRuntimeCache[$uid];
+        }
+
+        $objectManager = GeneralUtility::makeInstance(ObjectManager::class);
+        $backendUserRepository = $objectManager->get(BackendUserRepository::class);
+        /** @var \TYPO3\CMS\Extbase\Domain\Model\BackendUser $user */
+        $user = $backendUserRepository->findByUid($uid);
+        // $user may be NULL if user was deleted from DB, set it to empty string to always return a string
+        static::$usernameRuntimeCache[$uid] = $user === null ? '' : $user->getUserName();
+        return static::$usernameRuntimeCache[$uid];
+    }
+}