Pipes, Guards & Interceptors — Series 2

Preview — 3 of 10 questions

What does this pipe accept, and what happens for ?active=yes?

javascript

@Get()
findAll(@Query('active', ParseBoolPipe) active: boolean) {
  return this.catsService.findAll(active);
}

AIt accepts any non-empty string as true, so yes becomes true

BIt accepts the strings 'true' and 'false' (and real booleans), converting them to the matching boolean; yes is rejected with a 400 Bad Request

CIt accepts 1 and 0 only, so both true and yes are rejected

DIt coerces with Boolean(value), so every non-empty string becomes true

What does this achieve?

javascript

@Get(':id')
findOne(@Param('id', new ParseUUIDPipe({ version: '4' })) id: string) {}

AIt generates a UUID when the parameter is missing

BIt converts the string into a binary UUID object for the database driver

CIt has no runtime effect unless a global ValidationPipe is also registered

DIt rejects any id that is not a valid v4 UUID with a 400, so malformed identifiers never reach the service or the database

What is the scope of this registration?

javascript

@UsePipes(new ValidationPipe({ whitelist: true }))
@Controller('cats')
export class CatsController {
  @Post() create(@Body() dto: CreateCatDto) {}
  @Put(':id') update(@Body() dto: UpdateCatDto) {}
}

AEvery handler in this controller, for every argument that has a metatype to validate — one declaration instead of repeating the pipe on each method

BOnly the first handler declared in the class

CEvery controller in the same module

DNothing; @UsePipes() is valid on methods only

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