Mene ne ke ɗekoratoci kuma ana amfani da su ta yaya?

Question

Accepted Answer

**Dekorator** wata alokaci ne ta musamman (`@name`) da ta kara hali ko metadata ga jami'a, hanya, kadarori, ko paramita. Ita aje ne da runtime ke kira tare da burge da aka yiwa, yana ba ku damar lullubu ko bayananta ta faɗi.

```ts
// A simple method decorator that logs calls
function log(target: any, key: string, desc: PropertyDescriptor) {
  const original = desc.value;
  desc.value = function (...args: any[]) {     // wrap the original method
    console.log(`calling ${key} with`, args);
    return original.apply(this, args);
  };
}

class Service {
  @log
  fetch(id: number) { return { id }; }
}
new Service().fetch(1); // logs "calling fetch with [1]" then runs
```

Dekorator ya karbi halayen hanya kuma ta maye gurginsa da wrapper — halin ketare-ketare (shiryawa, ajiya, lokaci) ba tare da taɓa jiki na hanya ba.

## Waje da ka fi gani su: frameworks

```ts
@Controller("users")          // NestJS — declares a route controller
export class UsersController {
  @Get(":id")                 // maps GET /users/:id
  findOne(@Param("id") id: string) { return id; } // param decorator injects the route param
}

@Entity()                     // TypeORM — maps a class to a DB table
class User { @Column() name: string; }
```

NestJS, Angular, TypeORM, da class-validator an gina su a kusa da dekoratoci don DI, routing, ORM mapping, da tabbatarwa.

## Ɗabi biyu (mahimmi)

```json
{ "experimentalDecorators": true, "emitDecoratorMetadata": true }
```

**Tsohuwar (gwaje-gwaje)** dekoratoci a sama ne abin da Nest/Angular/TypeORM suke dogara a jiya. Akwai kuma sabuwar **TC39 Stage-3 dekoratoci** (TS 5+) tare da abin hannun yau dua, wadda ita ce zatarun gida — amma yawancin frameworks da ake da shi har yanzu suke amfani da nisa.

## Me ya dalanta

Dekoratoci suna buɗe tsattsauran, faɗi meta-programming — sare na servers frameworks da ORMs.

Sanin hañin aiki biyu (hanya ta gida burge) da kuma tsoho-vs-sabuwa raba ita ce dole don aiki a NestJS/Angular ecosystem.