NestJS项目中Reports Controller无法注入Users Service问题求助

我正在开发一个NestJS小型项目，包含reports和users两个独立模块，各自拥有Service、Controller和Repository。reports与users为多对一关系，我想给reports添加user属性，于是尝试在ReportsController中注入UsersService，但遇到了依赖注入错误。

相关代码 #

users.service.ts #

import { BadRequestException, Injectable, NotFoundException } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';
import { Users } from './users.entity';

@Injectable()
export class UsersService {
    constructor(
        @InjectRepository(Users) private userRepository: Repository<Users>
    ) {
        userRepository.remove = userRepository.softRemove;
        userRepository.delete = userRepository.softDelete;
    }
    createUser(body: object) {
        const instance = this.userRepository.create(body);
        return this.userRepository.save(instance);
    }

    find(query: object) {
        return this.userRepository.find({ "where": query })
    }

    findOne(id: any) {
        if (!id) {
            throw new BadRequestException('Id not found')
        }
        return this.userRepository.findOne({ "where": { "id": id } });
    }

    async update(id: string, record: Partial<Users>) {
        var user = await this.findOne(id);
        if (!user) {
            return new NotFoundException('User Not Found');
        }
        return this.userRepository.save(Object.assign(user, record));
    }

    async delete(id: string) {
        var user = await this.findOne(id);
        if (!user || user === null) {
            throw new NotFoundException('User Not Found');
        }
        else {
            this.userRepository.remove(user)
            return "Successfully deleted"
        }
    }
}

reports.controller.ts #

import { Body, ClassSerializerInterceptor, Controller, Post, Session, UseGuards, UseInterceptors } from '@nestjs/common';
import { UsersService } from 'src/users/users.service';
import { ReportsService } from './reports.service';

@Controller('reports')
export class ReportsController {
    constructor(
        private reportsService: ReportsService,
        private usersService: UsersService
    ) { }
}

错误说明 #

报错核心是UsersService无法被解析，原因是NestJS模块默认隔离，ReportsModule无权直接访问UsersModule内的服务。

解决步骤 #

1. 在UsersModule中导出UsersService
   修改users.module.ts，将UsersService加入exports数组，开放给其他模块使用：

   import { Module } from '@nestjs/common';
   import { TypeOrmModule } from '@nestjs/typeorm';
   import { Users } from './users.entity';
   import { UsersService } from './users.service';
   import { UsersController } from './users.controller';
   
   @Module({
     imports: [TypeOrmModule.forFeature([Users])],
     providers: [UsersService],
     controllers: [UsersController],
     exports: [UsersService] // 新增导出配置
   })
   export class UsersModule {}
   

2. 在ReportsModule中导入UsersModule
   修改reports.module.ts，将UsersModule加入imports数组，让ReportsModule能获取到UsersService：

   import { Module } from '@nestjs/common';
   import { TypeOrmModule } from '@nestjs/typeorm';
   import { Reports } from './reports.entity';
   import { ReportsService } from './reports.service';
   import { ReportsController } from './reports.controller';
   import { UsersModule } from '../users/users.module'; // 导入UsersModule
   
   @Module({
     imports: [TypeOrmModule.forFeature([Reports]), UsersModule], // 新增UsersModule导入
     providers: [ReportsService],
     controllers: [ReportsController]
   })
   export class ReportsModule {}
   

3. 验证根模块配置
   确保AppModule中同时导入了UsersModule和ReportsModule，保证两个模块都能被NestJS正常加载。

原理说明 #

NestJS模块采用隔离设计，模块内的Provider默认仅在本模块可见。要跨模块使用Provider，必须先在其所属模块的exports中声明导出，再在目标模块的imports中导入该模块，才能完成依赖注入。

内容的提问来源于stack exchange，提问作者user20181423