Dependency Injection Pattern

The Dependency Injection (DI) pattern is a software design pattern that promotes loose coupling and facilitates the management of dependencies between objects. In this pattern, the dependencies of a class are provided externally rather than being created internally within the class itself. By injecting dependencies, the class becomes more flexible, reusable, and easier to test and maintain.

• Name: Dependency Injection

• Type: Behavioral pattern

• Purpose: Manage dependencies between objects and promote loose coupling.

• Client: The class or component that depends on other objects.

• Service: The dependency that is required by the client.

• Injector: Responsible for creating and injecting the dependencies into the client.

In the above example, the UserService class depends on the UserRepository class to retrieve user data. Instead of creating an instance of UserRepository internally, the dependency is injected through the constructor of UserService. This allows the UserService to be decoupled from the specific implementation of UserRepository and enables easy substitution or extension of the repository.

• Promotes loose coupling between components, making them more modular and independent.

• Enhances testability by facilitating the use of mock objects or test doubles for dependencies during unit testing.

• Supports flexibility and extensibility by enabling easy substitution of dependencies with different implementations.

• Can introduce complexity, especially in larger applications with many dependencies.

• Requires careful management and configuration of dependencies, which can be challenging in complex scenarios.

• May require additional frameworks or tools to implement dependency injection effectively.

Note: The example provided demonstrates constructor injection, but there are other forms of dependency injection, such as setter injection and interface-based injection, which can be used depending on the specific requirements and design of the application.