Dependency Inversion Principle (DIP)

Overview

High-level modules should not depend on low-level modules. Both should depend on abstractions.

Classes should depend on interfaces, not concrete implementations. Dependencies should be injected, not instantiated internally.

When to Use

• Creating any class that uses external services
• Class uses database, email, file system, APIs
• Writing new ConcreteClass() inside another class
• Told "don't overcomplicate with DI"

The Iron Rule