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

Decorator	Validation
@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);
}

Related Pages

• DTO Design Patterns — DTOs
• Request Lifecycle — request flow
• Error Handling — errors