Controller Internals — Series 3

Preview — 3 of 10 questions

What do these three decorators store, and what consumes it?

javascript

@Get(':id')
findOne(@Param('id') id: string, @Query('full') full: string, @Headers('accept') accept: string) {}

AThree separate metadata keys, one per decorator kind, each read by its own binder

BA wrapper function per parameter, invoked with the request at call time

COne route-arguments metadata entry per parameter, recording a numeric paramtype (param, query, headers, body, …), the optional key and any pipes — which a single factory then reads at call time, switching on the paramtype to pull the value out of the request

DThe parameter's name, which the factory matches against properties of the request object

What do these two reads return?

javascript

const path = this.reflector.get<string>(PATH_METADATA, CatsController);
const method = this.reflector.get<number>(METHOD_METADATA, CatsController.prototype.findOne);

AThe controller's prefix ('cats') and the handler's HTTP method as the numeric RequestMethod enum value — the same metadata the router explorer reads when building the route table, which is why tooling can reconstruct the full route map from the class alone

BThe fully-resolved URL including the global prefix and version

Cundefined, because route metadata is consumed and removed during bootstrap

DThe compiled regular expression the router uses for matching

What status does the error path produce?

javascript

@Post('validate')
@HttpCode(200)
validate(@Body() dto: ValidateDto) {
  if (!dto.token) throw new BadRequestException('token required');
  return { ok: true };
}

A200, because @HttpCode applies to every response from the handler

B500, since the declared status conflicts with the exception's

C204, as no body was produced

D400 — @HttpCode sets the status for a successful return, while an exception's status comes from the exception itself as the filter layer builds the response

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