Clean-Code-Prinzipien für XOOPS

Übersicht

Clean Code ist Code, der leicht zu lesen, zu verstehen und zu warten ist. Dieser Leitfaden behandelt Clean-Code-Prinzipien, die speziell auf die XOOPS-Modulentwicklung angewendet werden.

Kernprinzipien

mindmap
  root((Clean Code))
    Readability
      Meaningful Names
      Small Functions
      Comments When Needed
    Simplicity
      Single Responsibility
      DRY Principle
      KISS Principle
    Maintainability
      Consistent Style
      Error Handling
      Testing

Aussagekräftige Namen

Variablen

// Bad
$d = new DateTime();
$u = $memberHandler->getUser($id);
$arr = [];

// Good
$createdDate = new DateTime();
$currentUser = $memberHandler->getUser($userId);
$publishedArticles = [];

Funktionen

// Bad
function process($data) { ... }
function handle($item) { ... }
function doStuff($x, $y) { ... }

// Good
function publishArticle(Article $article): void { ... }
function calculateTotalPrice(array $items): float { ... }
function sendNotificationEmail(User $user, string $subject): bool { ... }

Klassen

// Bad
class Manager { ... }
class Helper { ... }
class Utils { ... }

// Good
class ArticleRepository { ... }
class NotificationService { ... }
class PermissionChecker { ... }

Kleine Funktionen

Einzelverantwortung

// Bad - does too many things
function processArticle($data) {
    // Validate
    if (empty($data['title'])) {
        throw new Exception('Title required');
    }
    // Save
    $article = new Article();
    $article->setTitle($data['title']);
    $this->repository->save($article);
    // Notify
    $this->mailer->send($article->getAuthor(), 'Article published');
    // Log
    $this->logger->info('Article created');
    return $article;
}

// Good - each function does one thing
function validateArticleData(array $data): void
{
    if (empty($data['title'])) {
        throw new ValidationException('Title required');
    }
}

function createArticle(array $data): Article
{
    $this->validateArticleData($data);
    return Article::create($data['title'], $data['content']);
}

function publishArticle(Article $article): void
{
    $this->repository->save($article);
    $this->notifyAuthor($article);
    $this->logArticleCreation($article);
}

Funktionslänge

Halten Sie Funktionen kurz - idealerweise unter 20 Zeilen:

// Good - focused function
public function getPublishedArticles(int $limit = 10): array
{
    $criteria = new CriteriaCompo();
    $criteria->add(new Criteria('status', 'published'));
    $criteria->setSort('published_at');
    $criteria->setOrder('DESC');
    $criteria->setLimit($limit);

    return $this->repository->getObjects($criteria);
}

DRY-Prinzip (Don’t Repeat Yourself)

Allgemeinen Code extrahieren

// Bad - repeated code
function getActiveUsers() {
    $criteria = new CriteriaCompo();
    $criteria->add(new Criteria('level', 0, '>'));
    $criteria->setSort('uname');
    return $this->userHandler->getObjects($criteria);
}

function getActiveAdmins() {
    $criteria = new CriteriaCompo();
    $criteria->add(new Criteria('level', 0, '>'));
    $criteria->add(new Criteria('is_admin', 1));
    $criteria->setSort('uname');
    return $this->userHandler->getObjects($criteria);
}

// Good - shared logic extracted
function getUsers(CriteriaCompo $criteria): array
{
    $criteria->add(new Criteria('level', 0, '>'));
    $criteria->setSort('uname');
    return $this->userHandler->getObjects($criteria);
}

function getActiveUsers(): array
{
    return $this->getUsers(new CriteriaCompo());
}

function getActiveAdmins(): array
{
    $criteria = new CriteriaCompo();
    $criteria->add(new Criteria('is_admin', 1));
    return $this->getUsers($criteria);
}

Fehlerbehandlung

Ausnahmen richtig verwenden

// Bad - generic exceptions
throw new Exception('Error');

// Good - specific exceptions
throw new ArticleNotFoundException($articleId);
throw new PermissionDeniedException('Cannot edit article');
throw new ValidationException(['title' => 'Title is required']);

Fehler elegant behandeln

public function findArticle(string $id): ?Article
{
    try {
        return $this->repository->findById($id);
    } catch (DatabaseException $e) {
        $this->logger->error('Database error finding article', [
            'id' => $id,
            'error' => $e->getMessage()
        ]);
        throw new ServiceException('Unable to retrieve article', 0, $e);
    }
}

Kommentare

Wann man kommentieren sollte

// Bad - obvious comment
// Increment counter
$counter++;

// Good - explains why, not what
// Cache for 1 hour to reduce database load during peak traffic
$cache->set($key, $data, 3600);

// Good - documents complex algorithm
/**
 * Calculate article relevance score using TF-IDF algorithm.
 * Higher scores indicate better match with search terms.
 */
function calculateRelevanceScore(Article $article, array $terms): float
{
    // ...
}

Code-Organisation

Klassenstruktur

class ArticleService
{
    // 1. Constants
    private const MAX_TITLE_LENGTH = 255;

    // 2. Properties
    private ArticleRepository $repository;
    private EventDispatcher $events;

    // 3. Constructor
    public function __construct(
        ArticleRepository $repository,
        EventDispatcher $events
    ) {
        $this->repository = $repository;
        $this->events = $events;
    }

    // 4. Public methods
    public function publish(Article $article): void { ... }
    public function archive(Article $article): void { ... }

    // 5. Private methods
    private function validateForPublication(Article $article): void { ... }
}

Clean-Code-Checkliste

Namen sind aussagekräftig und aussprechbar
Funktionen tun nur eine Sache
Funktionen sind klein (< 20 Zeilen)
Kein duplizierter Code
Ordnungsgemäße Fehlerbehandlung mit spezifischen Ausnahmen
Kommentare erklären “warum”, nicht “was”
Konsistente Formatierung und Stil
Keine magischen Zahlen oder Zeichenketten
Abhängigkeiten werden injiziert, nicht erstellt