Dependency injection (DI) je pattern, kdy objekty dostávají své závislosti zvenčí, místo aby si je samy vytvářely — zlepšuje testovatelnost, údržovatelnost a flexibilitu. V Androidu je Hilt (postavený na Daggeru) doporučovaný DI framework.
Co je DI a proč
WITHOUT DI: a class CREATES its own dependencies (tightly coupled, hard to test/change):
class UserRepo { val api = ApiService() } // creates its own dependency — rigid
WITH DI: dependencies are PROVIDED from outside (injected):
class UserRepo(val api: ApiService) // receives it → flexible, testable
→ Benefits: TESTABILITY (inject mocks/fakes in tests), DECOUPLING, easier to swap
implementations, centralized dependency management, less boilerplate (with a framework).
