midOOP
What is Dependency Injection in OOP?
Updated May 17, 2026
Short answer
Dependency Injection provides objects their dependencies instead of creating them internally.
Deep explanation
It decouples object creation from usage, improving testability and flexibility in system architecture.
Real-world example
Injecting database service into API controllers.
Common mistakes
- Using 'new' inside business logic classes.
Follow-up questions
- What are DI types?
- Why is DI important?