attac-t Skill: Registry
"Register once, resolve anywhere."
The Decision
Use Registry when:
- Need to add/remove implementations at runtime
- Strategies or handlers are resolved by identifier
- Plugin-like extensibility is required
- UI needs to display available options
Use Direct DI when:
- Single implementation per interface
- No runtime discovery needed
- Static, compile-time binding is fine
The Heuristic
Ask: "Do I need to discover or extend implementations at runtime?"
- Yes, dynamic → Registry
- No, fixed → Direct DI
The Quick Test
| Scenario | Use |
|---|---|
| User selects from available strategies | Registry |
| Third-party can add implementations | Registry |
Need all() or getOptions() methods |
Registry |
| One implementation, injected directly | Direct DI |
| Known at compile time | Direct DI |
The Pattern
class StrategyRegistry {
public function register(StrategyInterface $s): void;
public function resolve(string $id): ?StrategyInterface;
public function all(): Collection;
}
Real-World Examples
For concrete examples from Laravel, Spatie, and production code, see examples.md.