Decorator Pattern Generator

Creates Decorator pattern infrastructure for dynamically adding behavior to objects.

When to Use

| Scenario | Example | |----------|---------| | Cross-cutting concerns | Logging, caching, metrics | | Transparent wrapping | Add behavior without changing interface | | Stackable features | Multiple decorators combined | | Runtime behavior | Dynamic feature addition |

Component Characteristics

Component Interface

• Defines core operations
• Shared by concrete and decorators
• Enables transparent wrapping

Abstract Decorator

• Wraps component
• Delegates to wrapped object
• Base for concrete decorators

Concrete Decorators

• Add specific behavior
• Before/after wrapped call
• Can be stacked

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Generation Process

Step 1: Generate Component Interface

Path: src/Domain/{BoundedContext}/

1. {Name}Interface.php — Core operations contract

Step 2: Generate Abstract Decorator

Path: src/Domain/{BoundedContext}/Decorator/

1. Abstract{Name}Decorator.php — Base decorator with delegation

Step 3: Generate Concrete Decorators

Path: src/Infrastructure/{BoundedContext}/Decorator/

1. Logging{Name}Decorator.php — Logging behavior
2. Caching{Name}Decorator.php — Caching behavior
3. Metrics{Name}Decorator.php — Performance metrics
4. Transactional{Name}Decorator.php — Transaction wrapping

Step 4: Generate Factory (Optional)

Path: src/Infrastructure/{BoundedContext}/

1. {Name}Factory.php — Stack decorators in correct order

Step 5: Generate Tests

1. {Feature}{Name}DecoratorTest.php — Individual decorator tests

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File Placement

| Component | Path | |-----------|------| | Interface | src/Domain/{BoundedContext}/ | | Abstract Decorator | src/Domain/{BoundedContext}/Decorator/ | | Infrastructure Decorators | src/Infrastructure/{BoundedContext}/Decorator/ | | Factory | src/Infrastructure/{BoundedContext}/ | | Unit Tests | tests/Unit/Infrastructure/{BoundedContext}/Decorator/ |

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Naming Conventions

| Component | Pattern | Example | |-----------|---------|---------| | Interface | {Name}Interface | OrderServiceInterface | | Abstract Decorator | Abstract{Name}Decorator | AbstractOrderServiceDecorator | | Concrete Decorator | {Feature}{Name}Decorator | LoggingOrderServiceDecorator | | Factory | {Name}Factory | OrderServiceFactory | | Test | {ClassName}Test | LoggingOrderServiceDecoratorTest |

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Quick Template Reference

Abstract Decorator

abstract class Abstract{Name}Decorator implements {Name}Interface
{
    public function __construct(
        protected readonly {Name}Interface $wrapped
    ) {}

    public function {operation}({params}): {returnType}
    {
        return $this->wrapped->{operation}({args});
    }
}

Concrete Decorator

final readonly class {Feature}{Name}Decorator extends Abstract{Name}Decorator
{
    public function __construct(
        {Name}Interface $wrapped,
        private {Dependency} $dependency
    ) {
        parent::__construct($wrapped);
    }

    public function {operation}({params}): {returnType}
    {
        {beforeBehavior}
        $result = parent::{operation}({args});
        {afterBehavior}
        return $result;
    }
}

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Usage Example

// Stack decorators in order
$service = new TransactionalOrderServiceDecorator(
    new CachingOrderServiceDecorator(
        new MetricsOrderServiceDecorator(
            new LoggingOrderServiceDecorator(
                $baseService,
                $logger
            ),
            $metrics
        ),
        $cache
    ),
    $transaction
);

// Use normally - all decorators execute
$order = $service->create($command);

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Common Decorators

| Decorator | Purpose | |-----------|---------| | Logging | Log method calls and results | | Caching | Cache expensive operations | | Metrics | Collect performance metrics | | Transaction | Wrap in database transaction | | Retry | Retry failed operations | | CircuitBreaker | Protect from cascading failures | | Validation | Validate inputs before execution |

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Anti-patterns to Avoid

| Anti-pattern | Problem | Solution | |--------------|---------|----------| | Missing Interface | Can't swap decorators | Use shared interface | | Leaky Abstraction | Decorator-specific methods | Keep interface clean | | Order Dependency | Wrong stacking order | Document decorator order | | Heavy Decorators | Too much logic | Keep decorators focused | | No Abstract | Code duplication | Create abstract decorator |

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References

For complete PHP templates and examples, see:

• references/templates.md — Abstract Decorator, Concrete Decorator, Interface templates
• references/examples.md — Logging, Caching, Metrics, Transaction decorators and tests