Menene controllers a cikin NestJS?

Question

Accepted Answer

**Controllers** suna kula da HTTP requests na gida da kuma suna dawowa da amsa. Suna bayyana hanyoyin bantawa na aikinka da kuma suna aiki azaman wurin shigarwa — suna karba bukatun, suna fitar da bayanai, suna iyo wa sabis, da kuma suna bada sakonnin. Suna kiyaye abubuwan tafiyar hanya daga tunani na gida.

## Yasa ya zama mahalaci

```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);
  }
}
```

## Yadda ya aiki: masu suzumari suna taswira hanyoyin zuwa ayyuka

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

Masu suzumari suna ɗaukar hanyoyin jigon aiki zuwa hanyoyin HTTP ta hanyar bayani — tsarkacce kuma mai karanta, babu jiyya na taswira.

## Masu suzumari na parameter suna cire bayanai daga bukatun

```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)
) {}
```

Masu suzumari na parameter na Nest (`@Param`, `@Query`, `@Body`, `@Headers`) suna cire bayanai da kice-kice - babu jiyya na parsing na `req`.

## Kontroller su kamata su kasance BAKIN CIKI

```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
```

Mihin kyau: kiyaye kontroller **bakin ciki** — suna kula da abubuwan HTTP (tafiyar hanya, fitar da bayanai, dawowa da amsa) da kuma suna iyo wa duk tunani na gida zuwa **sabis**. Wannan rarrabuwar taba dauke da code mai sirbani da tsari.

## Yasa ya zama mahalaci

Kontroller wata muhimmiyar gida na NestJS ne — wurin shigarwa ga duk HTTP requests kuma inda aka bayyana hanyoyin API na ka.

Sanin yadda masu suzumari (`@Controller`, `@Get`/`@Post`, `@Param`/`@Body`/`@Query`) ke taswira hanyoyin zuwa hanyoyin HTTP kuma ke cire bayanai daga bukatun ta hanyar bayani muhimmin ilimi na NestJS koyashe — haka ne kake gini kowane endpoint.

Da mahimmanci kuma shine ƙa'idar kiyaye kontroller **bakin ciki** (kula da abubuwan HTTP kawai da kuma iyo wa tunani na gida zuwa sabis masu dauke), wanda ke nuna falsafar rarrabuwar abubuwan NestJS da ke ajiye code mai karewa da sirbani.

Kontroller, tare da sabis da gida, suna samar da tsarin sari na kowane aikinka na NestJS, wanda ke sa wajibar saninsanin daga farko.