Strategy Pattern (Symfony)

Use when

• One operation has several interchangeable algorithms chosen at runtime, such as payment providers or export formats.
• A switch or match on a type string keeps growing.
• New variants must be added without editing the code that selects them.

Default workflow

1. Define the strategy interface, with a supports() method or a key per strategy.
2. Tag every implementation through #[AutoconfigureTag] on the interface or on each class.
3. Inject them with #[AutowireIterator] to try each in order, or #[AutowireLocator] to fetch one by key.
4. Set priorities where evaluation order matters, and register a fallback strategy.
5. Test each strategy alone, and the selector with fakes.

Guardrails

• The selector fails explicitly when no strategy supports the input.
• Keep strategies stateless and independent of each other.
• Two cases that will not grow do not need the pattern: a match is enough.