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Pipe Validation Deep Dive

Input validation and transformation using NestJS pipes.

Global Validation Pipe​

// main.ts
app.useGlobalPipes(
  new ValidationPipe({
    whitelist: true, // Strip unknown properties
    forbidNonWhitelisted: true, // Throw on unknown properties
    transform: true, // Auto-transform payloads to DTO instances
    transformOptions: {
      enableImplicitConversion: true,
    },
  }),
);

Validation Flow​

Common Decorators​

DecoratorValidation
@IsString()Must be string
@IsNotEmpty()Cannot be empty
@IsEmail()Valid email
@IsUUID('4')Valid UUID v4
@IsEnum(MyEnum)Must be enum member
@IsDateString()ISO 8601 date string
@IsOptional()Skip if undefined
@ValidateNested()Validate nested object
@Type(() => Class)Transform to class
@Transform(fn)Custom transformation

Custom Pipe​

@Injectable()
export class TenantOrganizationPipe implements PipeTransform {
  transform(value: any) {
    const tenantId = RequestContext.currentTenantId();
    return { ...value, tenantId };
  }
}

UUID Parameter Pipe​

@Get(':id')
async findOne(@Param('id', new ParseUUIDPipe()) id: string) {
  return this.service.findOneByIdString(id);
}