Dependency Inversion Principle

Applying DIP allows high-level modules to be insulated from low-level implementation details, letting infrastructure evolve independently. Swappable injected implementations allow core logic to remain unchanged. Dependency injection lets UserService avoid knowing which notification or payment implementation is used. Dependency injection removes the need for components to understand how their dependencies are built. Moving dependencies out of the method lets the method signature focus on the data needed for the method's real job. Dependency injection can make class splitting feel less costly by removing manual dependency-passing work. IoC is directly connected to the Dependency Inversion Principle. The Dependency Inversion Principle is the D in SOLID. The Dependency Inversion Principle states that high-level modules should not depend on low-level modules; both should depend on abstractions, and abstractions should not depend on details. Dependency injection is the primary practical mechanism by which IoC operates. The principle says high-level and low-level modules should both depend on abstractions instead of high-level modules depending directly on low-level modules. Implementati…