Apa iku kontroler ing NestJS?

Question

Accepted Answer

**Kontroler** nangani **HTTP request** ing mlebu lan ngirim balesan. Dheweke nemtokake rute aplikasine lan tumindak minangka titik entri — nampa request, ngekstrak data, ndelega menyang layanan, lan ngirim asil. Dheweke njaga kasunyatan rute kapisah saka logika bisnis.

## Nemtokake kontroler

```ts
import { Controller, Get, Post, Body, Param } from "@nestjs/common";

@Controller("users")          // the route PREFIX → all routes start with /users
export class UsersController {
  constructor(private usersService: UsersService) {}   // inject a service via DI

@Get()                       // GET /users
  findAll() {
    return this.usersService.findAll();
  }

@Get(":id")                  // GET /users/:id
  findOne(@Param("id") id: string) {        // extract the route param
    return this.usersService.findOne(id);
  }

@Post()                      // POST /users
  create(@Body() dto: CreateUserDto) {       // extract the request body
    return this.usersService.create(dto);
  }
}
```

## Carane gumana: dekorator nggambarake metode menyang rute

```text
@Controller("users") → route prefix /users
@Get() / @Post() / @Put() / @Patch() / @Delete() → HTTP method + sub-path
Combined: @Get(":id") inside @Controller("users") → GET /users/:id
```

Dekorator kanthi deklaratif ngandhangi metode kelas menyang rute HTTP — resik lan gampang diwaca, ora ana pendaftaran rute manual.

## Dekorator parameter ngekstrak data request

```ts
@Get(":id")
example(
  @Param("id") id: string,        // route parameter (/users/:id)
  @Query("sort") sort: string,    // query string (?sort=name)
  @Body() body: CreateUserDto,    // request body
  @Headers("authorization") auth: string,  // a header
  @Req() req: Request,            // the raw request object (rarely needed)
) {}
```

Dekorator parameter Nest (`@Param`, `@Query`, `@Body`, `@Headers`) kanthi resik ngekstrak persis data sing dibutuhake — ora ana pamondokan manual saka `req`.

## Kontroler kudu TIPIS

```ts
// ✅ controller delegates to a service — stays thin
@Post()
create(@Body() dto: CreateUserDto) {
  return this.usersService.create(dto);   // business logic lives in the SERVICE
}
// ❌ don't put database queries / business logic directly in the controller
```

Praktik paling apik: jaga kontroler **tipis** — dheweke nangani kasunyatan HTTP (rute, ngekstrak data, ngirim balesan) lan ndelega kabeh logika bisnis menyang **layanan**. Pemisahan iki njaga kode bisa diuji lan terorganisir.

## Mengapa iku penting

Kontroler minangka blok bangunan fondamental NestJS — titik entri kanggo kabeh HTTP request lan papan rute API nemtokake.

Paham carane dekorator (`@Controller`, `@Get`/`@Post`, `@Param`/`@Body`/`@Query`) nggambarake metode menyang rute lan ngekstrak data request kanthi deklaratif minangka katrangan penting saben dina NestJS — iki carane nggawe endpoint apa wae.

Sanederhanane penting minangka prinsip njaga kontroler **tipis** (nangani mung kasunyatan HTTP lan ndelega logika bisnis menyang layanan sing disuntikake), kang ngucapake filosofi pemisahan kasunyatan NestJS lan njaga kode bisa direwang lan diuji.

Kontroler, bebarengan layanan lan modul, mbentuk struktur inti saben aplikasi NestJS, nggawe dheweke penting dipaham wiwit wiwitan.