Mene pipes kuma yadda validation ke aiki?

Question

Accepted Answer

**Pipes** sune azuzuwan da **suke canza ko bada shaida** kan babbar data kafin ya isa ga ɗan sadarwanin hanyar. Suna aiki akan jigogon hanyoyin sarrafa — ko suna canza su (misali string → number) ko suna bada shaida (suna ƙin bayar da data mara inganci). Bada shaida a cikin NestJS an gina shi akan pipes.

## Pipes na canja da aka gina

```ts
@Get(":id")
findOne(@Param("id", ParseIntPipe) id: number) {    // transforms "5" (string) → 5 (number)
  // id is guaranteed to be a number; non-numeric input → 400 error automatically
  return this.usersService.findOne(id);
}
// other built-ins: ParseBoolPipe, ParseUUIDPipe, ParseArrayPipe, DefaultValuePipe
```

Pipes masu canja suna canza shigar data zuwa nau'in daidai (route params/query koyaushe sune jeri), suna gazawa da 400 idan canja ba zai yiwu ba.

## ValidationPipe — bada shaida na DTO ta atomatik

```ts
// enable globally in main.ts
app.useGlobalPipes(new ValidationPipe({
  whitelist: true,              // remove properties not declared in the DTO
  forbidNonWhitelisted: true,   // throw if unknown properties are present
  transform: true,              // turn plain objects into DTO instances, convert types
}));
```

```ts
// with a DTO using class-validator decorators:
export class CreateUserDto {
  @IsEmail() email: string;
  @MinLength(8) password: string;
}

@Post()
create(@Body() dto: CreateUserDto) {   // ValidationPipe validates the body automatically
  // if invalid → 400 with details, BEFORE this runs
}
```

`ValidationPipe` tana karanta ƙwarangwar `class-validator` na DTO kuma ta bada shaida kan data masu zuwa ta atomatik — tana dawo da cikakken kuskure na 400 idan rashin nasara, don haka ɗan sadarwanin ku kawai zai karbi data mai inganci.

## Yadda pipes ke kudu a cikin ragin buƙatun

```text
Request → ...middleware/guards/interceptors... → PIPES (transform/validate) → Handler
Pipes run JUST BEFORE the route handler, operating on its method arguments.
```

## Pipes na mutum-mutum

```ts
@Injectable()
export class TrimPipe implements PipeTransform {
  transform(value: any) {
    return typeof value === "string" ? value.trim() : value;   // custom transformation
  }
}
// usage: @Body(TrimPipe) ...
```

Kun aiwatar da hanyar `transform()` ta `PipeTransform` don jiya bada shaida na mutum-mutum/canja logic.

## Aiwatar da pipes a matakai daban-daban

```ts
@UsePipes(new ValidationPipe())      // method or controller level
@Param("id", ParseIntPipe)            // parameter level
app.useGlobalPipes(new ValidationPipe())   // global (most common for validation)
```

## Mene ya kamata

Pipes shine babbar fasalin NestJS don shawo kan shigar ta aminci, kuma sune tushen tsarin **validation** na framework.

Tuntunin su shine mahimmanci saboda kusan kowane API endpoint yana buƙatar bada shaida kuma canza shigar: pipes na canja (`ParseIntPipe`, jne.) suna tiyata cewa sigar sune nau'in daidai, kuma — mafi mahimmanci — **`ValidationPipe`** haɗe da DTOs suna ba da bada shaida ta atomatik, mai bayani na buƙatun jiki a gida `class-validator` ƙa'idodi, suna ƙin bayar da data mara inganci ko masu cuci da kudi kada ta isa gidan kasuwancin ku da klyarau kuskure *kafin* ta isa aiwatar da kasuwanci.

Hakan yana muhimmanci ga jiya aminci (bada shaida/tsabtace babbar data, cire fasaliloli mara buƙata) kuma karfi (handlers kawai suna karbi data mai inganci).

Sanin yadda za a kunna global validation pipe tare da zaɓubbukan daidai (`whitelist`, `transform`), amfani da pipes na canja da aka gina, kuma rubuta pipes na mutum-mutum shine tushe ga gina aminci, mabani NestJS APIs — pipes kuma bada shaida ayyukan yau-yau, kayyiyar la'akari azuzuwan a cikin framework.