create-flyweight

Flyweight Pattern Generator

Creates Flyweight pattern infrastructure for memory optimization through object sharing.

When to Use

Scenario	Example
Large number of similar objects	Icons, glyphs, particles
Memory constraints	Mobile apps, embedded systems
Immutable shared state	Currency codes, tax rates
Performance optimization	Reduce object creation overhead

Component Characteristics

Flyweight Interface

• Defines operations
• Accepts extrinsic state as parameters

ConcreteFlyweight

• Stores intrinsic state (shared)
• Immutable
• Reusable across contexts

FlyweightFactory

• Creates and manages flyweights
• Returns existing or new flyweight
• Ensures sharing

---

Generation Process

Step 1: Generate Flyweight Interface

Path: src/Domain/{BoundedContext}/

1. {Name}Interface.php — Operations contract

Step 2: Generate ConcreteFlyweight

Path: src/Domain/{BoundedContext}/

1. {Name}Flyweight.php — Shared object

Step 3: Generate FlyweightFactory

Path: src/Domain/{BoundedContext}/Factory/ or src/Infrastructure/

1. {Name}FlyweightFactory.php — Manages flyweights

Step 4: Generate Tests

1. {ClassName}Test.php — Flyweight behavior and sharing verification

---

File Placement

Component	Path
Flyweight Interface	src/Domain/{BoundedContext}/
ConcreteFlyweight	src/Domain/{BoundedContext}/
FlyweightFactory	src/Domain/{BoundedContext}/Factory/
Unit Tests	tests/Unit/Domain/{BoundedContext}/

---

Naming Conventions

Component	Pattern	Example
Flyweight Interface	{Name}Interface	CurrencyInterface
ConcreteFlyweight	{Name}Flyweight	CurrencyFlyweight
FlyweightFactory	{Name}FlyweightFactory	CurrencyFlyweightFactory
Test	{ClassName}Test	CurrencyFlyweightTest

---

Quick Template Reference

Flyweight

final readonly class {Name}Flyweight implements {Name}Interface
{
    public function __construct(
        private string $intrinsicState
    ) {}

    public function {operation}(string $extrinsicState): {returnType}
    {
        return {combine intrinsic and extrinsic state};
    }
}

FlyweightFactory

final class {Name}FlyweightFactory
{
    private array $flyweights = [];

    public function getFlyweight(string $key): {Name}Interface
    {
        if (!isset($this->flyweights[$key])) {
            $this->flyweights[$key] = new {Name}Flyweight($key);
        }

        return $this->flyweights[$key];
    }

    public function getCount(): int
    {
        return count($this->flyweights);
    }
}

---

Usage Example

$factory = new CurrencyFlyweightFactory();

// Same object returned
$usd1 = $factory->getFlyweight('USD');
$usd2 = $factory->getFlyweight('USD');

assert($usd1 === $usd2); // true

// Format with extrinsic state
$usd1->format(100.50); // "$100.50"

---

Common Flyweights

Flyweight	Purpose
CurrencyFlyweight	Currency codes and symbols
IconFlyweight	UI icons
TaxRuleFlyweight	Tax rates by region
CharacterFlyweight	Text rendering glyphs
ColorFlyweight	Color palettes

---

Anti-patterns to Avoid

Anti-pattern	Problem	Solution
Mutable Flyweight	State changes affect all users	Make flyweights immutable
No Factory	Manual object management	Use flyweight factory
Large Intrinsic State	Memory not optimized	Keep intrinsic state minimal
Extrinsic in Flyweight	Not reusable	Pass extrinsic via parameters
Premature Optimization	Complexity without benefit	Profile first

---

References

For complete PHP templates and examples, see:

• references/templates.md — Flyweight, factory templates
• references/examples.md — Currency, icon, tax rule flyweights with unit tests