Design Patterns design critical
Dependency Injection
Dependency Injection (DI) is a technique for achieving Inversion of Control by supplying dependencies from outside rather than creating them internally. Covers constructor injection, DI containers, and scopes.
- Difficulty
- intermediate
- Read time
- 1 min read
- Version
- v1.0.0
- Confidence
- established
- Last updated
Quick Reference
Dependency Injection: Pass dependencies via constructor (preferred), not via new inside class. Benefits: testability (mock deps), loose coupling, flexible config. Use DI containers (InversifyJS, FastAPI Depends) for complex apps. Scopes: Singleton (shared), Request (per request), Transient (new each time).
Use When
- Building testable applications
- Decoupling classes from concrete implementations
- Configuring services at runtime
- Managing complex dependency graphs
Skip When
- Simple scripts with no dependencies
- Value objects or data classes
- Static utility functions
Dependency Injection
Dependency Injection (DI) is a technique for achieving Inversion of Control by supplying dependencies from outside rather than creating them internally. Covers constructor injection, DI containers, and scopes.