Samsetningarrót

Samsetningarrót is an Icelandic term that translates to "composition root" in English. It is a software design pattern used in the development of complex applications, particularly those employing the Dependency Injection (DI) principle. The primary purpose of the composition root is to centralize the creation and wiring of all objects (dependencies) within an application.

In a typical application, different parts of the code will require various objects to function. Without a composition root, these objects might be created in numerous scattered locations, leading to code duplication, tight coupling, and difficulty in managing dependencies. The composition root acts as a single entry point where the entire object graph of the application is constructed. This means that all services, factories, and other components are instantiated here and their dependencies are injected into them.

By consolidating object creation and dependency wiring in one place, the composition root significantly improves application maintainability and testability. Developers can easily see how different parts of the system are connected and can readily substitute implementations for testing purposes. It follows the principle of Inversion of Control, where the framework or composition root is responsible for creating and providing objects, rather than the objects themselves creating their dependencies. This pattern is often implemented at the application's startup phase before the main execution logic begins.