iOS Dependency Injection

Priority: P0

Implementation Workflow

1. Prefer initializer injection — Pass dependencies through init as the primary approach.
2. Inject protocols — Always depend on protocols instead of concrete classes for testability.
3. Choose a DI library — Use Factory for lightweight DI, Swinject for enterprise-grade container-based projects.
4. Apply correct scoping — Singleton for app-wide services (Auth, Network); Unique/Transient for ViewModels; Graph/Cached for feature flows.

See protocol-based DI and Factory registration examples

Anti-Patterns

• ❌ Global singleton access everywhere — inject services via initializer
• ❌ Resolver.resolve() inside business logic — pass dependencies via constructor
• ❌ Direct class instantiation — depend on protocols for testability

References

• Manual & Library DI Setup