如何在带有 HTML 渲染的 NestJs 中使用验证？

Question

NestJS uses validation with validation pipes and

@UsePipes(ValidationPipe)

If this fails it throws an exception. This is fine for REST APIs that return JSON.

How would one validate parameters when using HTML rendering and return

{ errors: ['First error'] }

to an hbs template?

Answer 1

You can create an Interceptor that transforms the validation error into an error response:

@Injectable()
export class ErrorsInterceptor implements NestInterceptor {
  intercept(
    context: ExecutionContext,
    call$: Observable<any>,
  ): Observable<any> {
    return call$.pipe(
        // Here you can map (or rethrow) errors
        catchError(err => ({errors: [err.message]}),
      ),
    );
  }
}

You can use it by adding @UseInterceptors(ErrorsInterceptor) to your controller or its methods.

Answer 2

Another approach (which as a newcomer, I find more approachable) is to use ExceptionFilter s like so:

import { ExceptionFilter, Catch, ArgumentsHost, HttpException } from '@nestjs/common';
import { Request, Response } from 'express';

@Catch(HttpException)
export class HttpExceptionFilter implements ExceptionFilter {
  catch(exception: HttpException, host: ArgumentsHost) {
    const ctx = host.switchToHttp();
    const response = ctx.getResponse<Response>();
    const exceptionResponse = exception.getResponse()

    response.render(YOUR_TEMPLATE_HERE, { errors: exceptionResponse["message"] })
  }
}

You can then add the @UseFilters(new HttpExceptionFilter()) decorator to the controller method.