CouplingBetweenObjects (CBO)

Emitted when a class depends on too many other classes. High coupling makes code harder to test, maintain, and reuse.

<?php
class Import extends ResourceObject
{
    use ResourceInject;
    use AuraSqlInject;

    public function __construct(
        private readonly ArticleRepository $articleRepo,
        private readonly ImageRepository $imageRepo,
        private readonly TagRepository $tagRepo,
        private readonly CategoryRepository $categoryRepo,
        private readonly AuthorRepository $authorRepo,
        private readonly Validator $validator,
        private readonly ImageProcessor $imageProcessor,
        private readonly NotificationService $notifier,
        // ... 22 dependencies
    ) {}

    public function onPost(): static
    {
        // 400 lines of business logic
        $this->validate();
        $this->processImages();
        $this->saveTags();
        $this->saveCategories();
        $this->notify();
        // ...
        return $this;
    }
}

Why this is bad

Hard to test: Need to mock 22 dependencies
Hard to understand: Too many responsibilities in one class
Fragile: Changes in any dependency may break this class
Violates Single Responsibility Principle: Class is doing too much

How to fix

Extract business logic to a dedicated service class:

<?php
class Import extends ResourceObject
{
    public function __construct(
        private readonly ImportService $service,
    ) {}

    public function onPost(string $id): static
    {
        $this->body = $this->service->import($id);

        return $this;
    }
}

The resource class now has a single responsibility: deciding what to return. All business logic is delegated to ImportService.

Threshold

Level	CBO Value
🍝 Piccolo	≤10
🍝🍝 Medio	11-13
🍝🍝🍝 Grande	14-17
🍝🍝🍝🍝 Mamma Mia!	18+