In NestJS, a provider adalah kelas apa wae sing bisa injected minangka dependency, lan a service yaiku jenis sing paling umum — kelas sing ngemot business logic. Nandai kelas nganggo @Injectable() nggawe dadi provider sing sistem DI NestJS bisa gawe lan inject.
import { Injectable } from "@nestjs/common";
@Injectable() // marks the class as a provider (injectable)
export class UsersService {
private users = [];
findAll() { return this.users; } // business logic
findOne(id: string) { return this.users.find(u => u.id === id); }
create(data) { this.users.push(data); return data; }
}
Decorator @Injectable() ngandhani NestJS yen kelas iki melu dependency injection — bisa diinjeksi menyang controllers utawa providers liyane.
@Controller("users")
export class UsersController {
// NestJS sees this parameter and INJECTS a UsersService instance automatically
constructor(private usersService: UsersService) {}
@Get()
findAll() {
return this.usersService.findAll(); // use the injected service
}
}
Kowe nyatakake dependency minangka parameter constructor; NestJS gawe lan nyupply instance — sampeyan ora keno nulis new UsersService().
@Module({
controllers: [UsersController],
providers: [UsersService], // register the provider so DI can resolve it
exports: [UsersService], // make it available to OTHER modules that import this one
})
export class UsersModule {}
Providers kudu didaftar ing array providers modulo supaya DI ngerti babagan iki, lan exports nuduhke menyang modulo liyane.
By default, NestJS creates ONE shared instance of each provider (singleton scope)
for the whole application → efficient, shared state.
(Other scopes exist: REQUEST-scoped, TRANSIENT — but singleton is the default.)
Controller → handles HTTP (routing, request/response)
Service → handles business logic (rules, data access, computations)
→ Separation makes logic REUSABLE (multiple controllers can use one service),
TESTABLE (test the service in isolation), and ORGANIZED.
Providers lan services yaiku inti saka arsitektur NestJS lan desain dependency-injection-driven e.
Services ngemot business logic aplikasi, kapisah saka controllers (sing nangani mung HTTP concerns) — pemisahan iki saka concerns nggawe logic bisa digunakake luwih akeh nang controllers, gampang di-test secara isolated, lan terorganisir kanthi apik.
Narti yen @Injectable() nandai kelas minangka injectable provider, yen providers didaftar ing modulo lan diinjeksi via constructors (DI gawe instances kanggo sampeyan), lan yen iku singletons secara default yaiku katrangan dasar NestJS saben dina.
Pola provider/service, digabung karo controllers lan modulo, yaiku tulang punggung saben aplikasi NestJS — ngusai iku penting banget kanggo mbangun back-ends sing terstruktur kanthi apik, mudah dimelihara, lan yaiku babagan pertama sing kudu sinau ing framework.