class-validator doesn't validate arrays - arrays

Question

I can't get the class-validator to work. It seems like I am not using it: everything works as if I didn't use class-validator. When sending a request with an incorrectly formatted body, I don't have any validation error, although I should.
My DTO:
import { IsInt, Min, Max } from 'class-validator';
export class PatchForecastDTO {
#IsInt()
#Min(0)
#Max(9)
score1: number;
#IsInt()
#Min(0)
#Max(9)
score2: number;
gameId: string;
}
My controller:
#Patch('/:encid/forecasts/updateAll')
async updateForecast(
#Body() patchForecastDTO: PatchForecastDTO[],
#Param('encid') encid: string,
#Query('userId') userId: string
): Promise<ForecastDTO[]> {
return await this.instanceService.updateForecasts(userId, encid, patchForecastDTO);
}
My bootstrap:
async function bootstrap() {
const app = await NestFactory.create(AppModule);
app.useGlobalPipes(new ValidationPipe());
await app.listen(PORT);
Logger.log(`Application is running on http://localhost:${PORT}`, 'Bootstrap');
}
bootstrap();
I can't find what's wrong. What did I miss?

Answer 1

In the current version of NestJS (7.6.14), validating a request body that is a JSON array is supported using the built in ParseArrayPipe.
#Post()
createBulk(
#Body(new ParseArrayPipe({ items: CreateUserDto }))
createUserDtos: CreateUserDto[],
) {
return 'This action adds new users';
}
See the official docs or the source code for more info.

Answer 2

NestJS actually does not support array validation out of the box. In order to validate an array, it must be wrapped in an object.
This way, I would not use a DTO corresponding to a list of items, but a DTO corresponding to an object that contains a list of items:
import { PatchForecastDTO } from './patch.forecast.dto';
import { IsArray, ValidateNested } from 'class-validator';
import { Type } from 'class-transformer';
export class PatchForecastsDTO {
#IsArray()
#ValidateNested() // perform validation on children too
#Type(() => PatchForecastDTO) // cast the payload to the correct DTO type
forecasts: PatchForecastDTO[];
}
And I would use that DTO in my controller:
#Patch('/:encid/forecasts/updateAll')
async updateForecast(
#Body() patchForecastsDTO: PatchForecastsDTO,
#Param('encid') encid: string,
#Query('userId') userId: string
): Promise<ForecastDTO[]> {
return await this.instanceService.updateForecasts(userId, encid, patchForecastsDTO);
}