Classes/Task/BatchResizeAdditionalFieldProvider.php
public function validateAdditionalFields(array &$submittedData, \TYPO3\CMS\Scheduler\Controller\SchedulerModuleController $parentObject)
    {
        $result = true;

        // Check for valid directories
        $directories = GeneralUtility::trimExplode(LF, $submittedData['scheduler_batchResize_directories'], true);
        foreach ($directories as $directory) {
            $absoluteDirectory = GeneralUtility::getFileAbsFileName($directory);
            if (!@is_dir($absoluteDirectory)) {
                $result = false;
                $parentObject->addMessage(
                    sprintf(
                        $GLOBALS['LANG']->sL('LLL:EXT:image_autoresize/Resources/Private/Language/locallang_mod.xlf:msg.invalidDirectories'),
                        $directory
                    ),
                    \TYPO3\CMS\Core\Messaging\FlashMessage::ERROR
                );
            }
        }

        $directories = GeneralUtility::trimExplode(LF, $submittedData['scheduler_batchResize_excludeDirectories'], true);
        foreach ($directories as $directory) {
            $absoluteDirectory = GeneralUtility::getFileAbsFileName($directory);
            if (!@is_dir($absoluteDirectory)) {
                $result = false;
                $parentObject->addMessage(
                    sprintf(
                        $GLOBALS['LANG']->sL('LLL:EXT:image_autoresize/Resources/Private/Language/locallang_mod.xlf:msg.invalidExcludeDirectories'),
                        $directory
                    ),
                    \TYPO3\CMS\Core\Messaging\FlashMessage::ERROR);
            }
        }

        return $result;
    }
public function validateAdditionalFields(array &$submittedData, \TYPO3\CMS\Scheduler\Controller\SchedulerModuleController $parentObject)
    {
        $result = true;

        // Check for valid directories
        $directories = GeneralUtility::trimExplode(LF, $submittedData['scheduler_batchResize_directories'], true);
        foreach ($directories as $directory) {
            $absoluteDirectory = GeneralUtility::getFileAbsFileName($directory);
            if (!@is_dir($absoluteDirectory)) {
                $result = false;
                $parentObject->addMessage(
                    sprintf(
                        $GLOBALS['LANG']->sL('LLL:EXT:image_autoresize/Resources/Private/Language/locallang_mod.xlf:msg.invalidDirectories'),
                        $directory
                    ),
                    \TYPO3\CMS\Core\Messaging\FlashMessage::ERROR
                );
            }
        }

        $directories = GeneralUtility::trimExplode(LF, $submittedData['scheduler_batchResize_excludeDirectories'], true);
        foreach ($directories as $directory) {
            $absoluteDirectory = GeneralUtility::getFileAbsFileName($directory);
            if (!@is_dir($absoluteDirectory)) {
                $result = false;
                $parentObject->addMessage(
                    sprintf(
                        $GLOBALS['LANG']->sL('LLL:EXT:image_autoresize/Resources/Private/Language/locallang_mod.xlf:msg.invalidExcludeDirectories'),
                        $directory
                    ),
                    \TYPO3\CMS\Core\Messaging\FlashMessage::ERROR);
            }
        }

        return $result;
    }
Checks if the given value is a string

@param array $submittedData Reference to the array containing the data submitted by the user
@param \TYPO3\CMS\Scheduler\Controller\SchedulerModuleController $parentObject Reference to the calling object (Scheduler's BE module)
@return boolean true if validation was ok (or selected class is not relevant), false otherwise