NestJS中DTO公共方法的最佳实践与职责边界

// customer.dto.ts (仅数据和验证)
import { IsString, IsNotEmpty } from 'class-validator';

export class CreateCustomerDto {
  @IsString()
  @IsNotEmpty()
  name: string;

  @IsString()
  @IsNotEmpty()
  email: string;
}

// lowercase-name.pipe.ts (自定义转换管道)
import { PipeTransform, Injectable, ArgumentMetadata, BadRequestException } from '@nestjs/common';

@Injectable()
export class LowercaseNamePipe implements PipeTransform {
  transform(value: any, metadata: ArgumentMetadata) {
    if (metadata.type === 'body' && value && typeof value === 'object' && 'name' in value) {
      if (typeof value.name === 'string') {
        value.name = value.name.toLowerCase();
      } else {
        throw new BadRequestException('Name must be a string.');
      }
    }
    return value;
  }
}

// customer.controller.ts (在控制器中使用管道)
import { Controller, Post, Body, UsePipes } from '@nestjs/common';
import { CreateCustomerDto } from './customer.dto';
import { LowercaseNamePipe } from './lowercase-name.pipe';

@Controller('customers')
export class CustomerController {
  @Post()
  @UsePipes(LowercaseNamePipe) // 应用自定义管道
  async createCustomer(@Body() createCustomerDto: CreateCustomerDto) {
    console.log(createCustomerDto.name); // 此时 name 已经是小写
    // ... 调用服务层处理业务逻辑
    return 'Customer created';
  }
}

// customer.dto.ts (使用 @Transform 装饰器)
import { IsString, IsNotEmpty } from 'class-validator';
import { Transform } from 'class-transformer';

export class CreateCustomerDto {
  @IsString()
  @IsNotEmpty()
  @Transform(({ value }) => typeof value === 'string' ? value.toLowerCase() : value) // 将 name 转换为小写
  name: string;

  @IsString()
  @IsNotEmpty()
  email: string;
}

// customer.controller.ts (控制器直接使用 DTO)
import { Controller, Post, Body, UsePipes, ValidationPipe } from '@nestjs/common';
import { CreateCustomerDto } from './customer.dto';

@Controller('customers')
export class CustomerController {
  @Post()
  // 结合 ValidationPipe 自动触发 class-transformer 的转换
  async createCustomer(@Body(new ValidationPipe({ transform: true })) createCustomerDto: CreateCustomerDto) {
    console.log(createCustomerDto.name); // 此时 name 已经是小写
    // ... 调用服务层处理业务逻辑
    return 'Customer created';
  }
}

// customer.service.ts
import { Injectable } from '@nestjs/common';
import { CreateCustomerDto } from './customer.dto';

@Injectable()
export class CustomerService {
  async create(customerData: CreateCustomerDto): Promise<any> {
    // 在这里执行数据库操作、发送事件等业务逻辑
    console.log('Creating customer with data:', customerData);
    // ... 实际的数据库插入逻辑
    return { id: 'some-id', ...customerData };
  }
}

// customer.controller.ts
import { Controller, Post, Body, UsePipes, ValidationPipe } from '@nestjs/common';
import { CreateCustomerDto } from './customer.dto';
import { CustomerService } from './customer.service';

@Controller('customers')
export class CustomerController {
  constructor(private readonly customerService: CustomerService) {}

  @Post()
  async createCustomer(@Body(new ValidationPipe({ transform: true })) createCustomerDto: CreateCustomerDto) {
    const newCustomer = await this.customerService.create(createCustomerDto);
    return newCustomer;
  }
}