NestJS Nest 无法解析 RolesService 的依赖项（+、+、？）

Question

您好，我正在使用 NestJS 框架（使用 MongoDB）进行编程，现在已经构建了一些模块。当我尝试从另一个模块导入模型时，它返回此错误：

Nest 无法解析 RolesService 的依赖项（+、+、？）。

现在，我已经实现了这样的代码：

app.module.ts

import { GroupsModule } from './groups/groups.module';
import { Module } from '@nestjs/common';
import { MongooseModule } from '@nestjs/mongoose';
import { UsersModule } from 'users/users.module';
import { RolesModule } from 'roles/roles.module';

@Module({
  imports: [
          MongooseModule.forRoot('mongodb://localhost:27017/example'),
          UsersModule,
          GroupsModule,
          RolesModule,
        ],
  providers: [],
})
export class AppModule {}

users.module.ts

import { Module } from '@nestjs/common';
import { MongooseModule } from '@nestjs/mongoose';

import { UsersController } from './users.controller';

import { UsersService } from './users.service';
import { RolesService } from 'roles/roles.service';

import { UserSchema } from './schemas/user.schema';
import { RoleSchema } from 'roles/schemas/role.schema';

@Module({
    imports: [
      MongooseModule.forFeature([{ name: 'User', schema: UserSchema }]),
      MongooseModule.forFeature([{ name: 'Role', schema: RoleSchema }]),
    ],
    controllers: [UsersController],
    providers: [UsersService, RolesService],
    exports: [UsersService],
  })

export class UsersModule {}

users.service.ts

import { Model } from 'mongoose';
import { ObjectID } from 'mongodb';
import { InjectModel } from '@nestjs/mongoose';
import { Injectable, HttpException, HttpStatus } from '@nestjs/common';

import { User } from './interfaces/user.interface';

@Injectable()
export class UsersService {
  constructor(@InjectModel('User') private readonly userModel: Model<User>) {}
}

groups.module.ts

import { MongooseModule } from '@nestjs/mongoose';

import { GroupsController } from './groups.controller';

import { RolesService } from '../roles/roles.service';
import { GroupsService } from './groups.service';

import { GroupSchema } from './schemas/group.schema';
import { UserSchema } from '../users/schemas/user.schema';
import { RoleSchema } from '../roles/schemas/role.schema';

@Module({
  imports: [
    MongooseModule.forFeature([{ name: 'Group', schema: GroupSchema }]),
    MongooseModule.forFeature([{ name: 'User', schema: UserSchema }]),
    MongooseModule.forFeature([{ name: 'Role', schema: RoleSchema }]),
  ],
  controllers: [GroupsController],
  providers: [GroupsService, RolesService],
  exports: [GroupsService],
})

groups.service.ts

import { Injectable, HttpException, HttpStatus } from '@nestjs/common';
import { InjectModel } from '@nestjs/mongoose';
import { ObjectID } from 'mongodb';
import { Model } from 'mongoose';

import { Group } from './interfaces/group.interface';
import { User } from '../users/interfaces/user.interface';

import { CreateGroupDto } from './dto/create-group.dto';
import { RolesDto } from 'roles/dto/roles.dto';
import { Role } from '../roles/interfaces/role.interface';

@Injectable()
export class GroupsService {
    constructor(@InjectModel('Group') private readonly groupModel: Model<Group>,
                @InjectModel('Role') private readonly roleModel: Model<Role>) {} }

roles.module.ts

import { Module } from '@nestjs/common';
import { MongooseModule } from '@nestjs/mongoose';

import { RolesController } from './roles.controller';

import { RolesService } from './roles.service';

import { RoleSchema } from './schemas/role.schema';
import { UserSchema } from '../users/schemas/user.schema';
import { GroupSchema } from '../groups/schemas/group.schema';

@Module({
    imports: [
      MongooseModule.forFeature([{ name: 'User', schema: UserSchema }]),
      MongooseModule.forFeature([{ name: 'Role', schema: RoleSchema }]),
      MongooseModule.forFeature([{ name: 'Group', schema: GroupSchema }]),
    ],
    controllers: [RolesController],
    providers: [RolesService],
    exports: [RolesService],
  })

export class RolesModule {}

roles.service.ts

import { Injectable, HttpException, HttpStatus } from '@nestjs/common';
import { InjectModel } from '@nestjs/mongoose';
import { ObjectID } from 'mongodb';
import { Model } from 'mongoose';

import { Role } from './interfaces/role.interface';
import { User } from '../users/interfaces/user.interface';
import { Group } from '../groups/interfaces/group.interface';

import { CreateRoleDto } from './dto/create-role.dto';
import { RolesDto } from './dto/roles.dto';

@Injectable()
export class RolesService {
    constructor( @InjectModel('Role') private readonly roleModel: Model<Role>,
                 @InjectModel('User') private readonly userModel: Model<User>,
                 @InjectModel('Group') private readonly groupModel: Model<Group> ) {} }

虽然用户和角色中的 DI 工作正常，但当我尝试在角色服务中导入组模型时出现错误。如果您发现任何错误，请告诉我，我已从用户组中遵循相同的架构，但遗憾的是看不到错误所在。

提前致谢。

更新：好的，我认为我的错误是当我尝试在模块外使用模块服务功能时。我的意思是我修改了（为了简化）我会这样修改代码：

users.module.ts

@Module({
    imports: [
      MongooseModule.forFeature([{ name: 'User', schema: UserSchema }]),
      RolesModule,
    ],
    controllers: [UsersController],
    providers: [UsersService, RolesService],
    exports: [UsersService],
  })

export class UsersModule {}

users.controller.ts

export class UsersController {

    constructor(private readonly usersService: UsersService,
                private readonly rolesService: RolesService){}

    async addRoles(@Param('id') id: string, @Body() userRolesDto: UserRolesDto): Promise<User> {
        try {
            return this.rolesService.setRoles(id, userRolesDto);
        } catch (e){
            const message = e.message.message;
            if ( e.message.error === 'NOT_FOUND'){
                throw new NotFoundException(message);
            } else if ( e.message.error === 'ID_NOT_VALID'){
                throw new BadRequestException(message);
            }
        }

    }

}

roles.module.ts

@Module({
    imports: [
      MongooseModule.forFeature([{ name: 'Role', schema: RoleSchema }]),
    ],
    controllers: [RolesController],
    providers: [RolesService],
    exports: [RolesService],
  })

export class RolesModule {}

roles.service.ts

@Injectable()
export class RolesService {
    userModel: any;
    constructor( @InjectModel('Role') private readonly roleModel: Model<Role> ) {}

    // SET USER ROLES
    async setRoles(id: string, rolesDto: RolesDto): Promise<User> {
        if ( !ObjectID.isValid(id) ){
            throw new HttpException({error: 'ID_NOT_VALID', message: `ID ${id} is not valid`, status: HttpStatus.BAD_REQUEST}, 400);
        }
        try {
            const date = moment().valueOf();
            const resp = await this.userModel.updateOne({
              _id: id,
            }, {
              $set: {
                  updated_at: date,
                  roles: rolesDto.roles,
              },
            });
            if ( resp.nModified === 0 ){
              throw new HttpException({ error: 'NOT_FOUND', message: `ID ${id} not found or entity not modified`, status: HttpStatus.NOT_FOUND}, 404);
            } else {
              let user = await this.userModel.findOne({ _id: id });
              user = _.pick(user, ['_id', 'email', 'roles', 'created_at', 'updated_at']);
              return user;
            }
        } catch (e) {
          if ( e.message.error === 'NOT_FOUND' ){
            throw new HttpException({ error: 'NOT_FOUND', message: `ID ${id} not found or entity not modified`, status: HttpStatus.NOT_FOUND}, 404);
          } else {
            throw new HttpException({error: 'ID_NOT_VALID', message: `ID ${id} is not valid`, status: HttpStatus.BAD_REQUEST}, 400);
          }
        }
    }

就是这样，当我尝试从 users.controller 使用 roles.service setRole 方法时，您可以看到它返回一个错误：

Nest 无法解析 RolesService (?) 的依赖关系。请确保索引 [0] 处的参数在当前上下文中可用。

我不明白问题出在哪里，因为我已经在 roles.module 中注入了 Role 模型并且它不理解它。事实上，如果我不创建从 users.module 到此依赖项的调用，一切都会好起来的。

有什么建议吗？

（我已经把stackoverflow的建议加红了，我不会再这样做了）

Answer 1

我认为问题在于您多次导入同一个模型，例如：

MongooseModule.forFeature([{ name: 'User', schema: UserSchema }]

并且还多次提供相同的服务：

providers: [RolesService]

我不会注入模型本身，而是注入封装模型的相应服务。然后你 export 模块中的服务并在需要的地方导入模块。所以RolesService 会注入UsersSerivce 而不是UserModel。

使用您当前的设置，您会遇到循环依赖。这可以通过fowardRef(() => UserService) 处理，但应尽可能避免，请参阅circular dependency docs。但是，这是否可以避免取决于您的业务逻辑。

如果你没有循环依赖，那么例如导出你的RolesService

@Module({
    imports: [MongooseModule.forFeature([{ name: 'Role', schema: RoleSchema }])]
    controllers: [RolesController],
    providers: [RolesService],
    exports: [RolesService],
  })

export class RolesModule {}

并在您想使用RolesService 的任何地方导入RolesModule，例如：

@Module({
    imports: [
      RolesModule,
      MongooseModule.forFeature([{ name: 'User', schema: UserSchema }])
    ],
    controllers: [UsersController],
    providers: [UsersService],
    exports: [UsersService],
  })