NestJs中的DTO是否可以继承？

Question

我有一个NestJs Get控制器，用于搜索员工列表。

@Controller('employee')
export class EmployeeController {
    private logger = new Logger('EmployeeController');
    constructor(private employeeService:EmployeeService){}

    @Get()
    @UsePipes(new ValidationPipe({ transform: true }))
    getEmployees(
        @Query() filter:GetEmployeesFilterDto
    ):Promise<Employee[]>{
        console.log(JSON.stringify(filter), filter.batch);
        return this.employeeService.getEmployees(filter);
    }
}

为了支持分页，该方法接受过滤器DTO以接受诸如批大小和页码之类的参数。看到这将成为其他DTO类的通用参数之后，我想到了创建基本过滤器DTO：

export class BaseQueryFilterDto{

    @IsOptional()
    @IsInt()
    @UsePipes(ParseIntPipe)
    batch:number;

    @IsOptional()
    @IsInt()
    @UsePipes(ParseIntPipe)
    skip:number;

}

然后为GetEmployeesFilterDto继承此DTO：

export class GetEmployeesFilterDto extends BaseQueryFilterDto{
    @IsOptional()
    @IsNotEmpty()
    search:string;

    @IsOptional()
    primarySupervisorId:string;

}

运行以下请求http://localhost:3000/employee?batch=30将引发以下异常：

[Nest] 27920   - 02/14/2020, 6:29:54 PM   [ExceptionsHandler] Cannot assign to read only property 'batch' of object '#<GetEmployeesFilterDto>' +606974ms
TypeError: Cannot assign to read only property 'batch' of object '#<GetEmployeesFilterDto>'
    at _loop_1 (C:\ng-proj\nestjs-tutorial\node_modules\class-transformer\TransformOperationExecutor.js:242:47)
    at TransformOperationExecutor.transform (C:\ng-proj\nestjs-tutorial\node_modules\class-transformer\TransformOperationExecutor.js:260:17)
    at ClassTransformer.plainToClass (C:\ng-proj\nestjs-tutorial\node_modules\class-transformer\ClassTransformer.js:17:25)    at Object.plainToClass (C:\ng-proj\nestjs-tutorial\node_modules\class-transformer\index.js:20:29)
    at ValidationPipe.transform (C:\ng-proj\nestjs-tutorial\node_modules\@nestjs\common\pipes\validation.pipe.js:55:41)
    at transforms.reduce (C:\ng-proj\nestjs-tutorial\node_modules\@nestjs\core\pipes\pipes-consumer.js:15:33)
    at process._tickCallback (internal/process/next_tick.js:68:7)

但是，当我将所有属性从超类移至GetEmployeesFilterDto时，如下所示：

export class GetEmployeesFilterDto extends BaseQueryFilterDto{
    @IsOptional()
    @IsNotEmpty()
    search:string;

    @IsOptional()
    primarySupervisorId:string;

    //Moved from BaseQueryFilterDto
    @IsOptional()
    @IsInt()
    @UsePipes(ParseIntPipe)
    batch:number;

    @IsOptional()
    @IsInt()
    @UsePipes(ParseIntPipe)
    skip:number;

}

请求成功运行。我在这里错过了什么吗，还是不能在NestJs中实现对控制器DTO的继承？

Answer 1

感谢@JayMcDoniel指出我不应该在属性上使用@UsePipes()。

这是最适合我的解决方案。

export class BaseQueryFilterDto{

    @IsOptional()
    @Type(() => Number)
    batch:number;

    @IsOptional()
    @Type(() => Number)
    skip:number;

}