Question

我正在尝试使用mongoose并通过跟随nestjs.com的连接来动态配置连接，但是在我的情况下，我需要注入工厂的服务无法解决。这是AppModule

@Injectable()
class Op implements MongooseOptionsFactory {
  constructor(
    @Inject(forwardRef(() => EndpointsService))
    private endpointsService: EndpointsService) {
  }

  createMongooseOptions(): MongooseModuleOptions {
    return {
      uri: this.endpointsService.loginMongoDb
    };
  }
}

@Module({
  imports: [
    MongooseModule.forRootAsync({
      useClass: Op,
      inject: [EndpointsService] // having this doesn't help either
    })
  ],
  controllers: [AppController, UserController],
  providers: [AppService, 
    EndpointsService, // is in the core module, but won't be seen
    UserService]
})
export class AppModule {
}

非常简单（忽略Op名称，稍后将其移至需要的位置）

这是EndpointsService

@Injectable()
export class EndpointsService {
  private readonly _loginApi: string;
  private readonly _loginMongoDb: string;

  constructor() {
....

但是ap无法启动，出现错误

[Nest] 83842   - 03/20/2020, 10:54:26 AM   [NestFactory] Starting Nest application...
[0] [Nest] 83842   - 03/20/2020, 10:54:26 AM   [InstanceLoader] MongooseModule dependencies initialized +14ms
[0] [Nest] 83842   - 03/20/2020, 10:54:26 AM   [ExceptionHandler] Nest can't resolve dependencies of the Op (?). Please make sure that the argument EndpointsService at index [0] is available in the MongooseCoreModule context.
[0] 
[0] Potential solutions:
[0] - If EndpointsService is a provider, is it part of the current MongooseCoreModule?
[0] - If EndpointsService is exported from a separate @Module, is that module imported within MongooseCoreModule?
[0]   @Module({
[0]     imports: [ /* the Module containing EndpointsService */ ]
[0]   })
[0]  +0ms

我还尝试在forwardRef类中使用不带Op的常规注入，但是结果是相同的。

我想念什么？

Answer 1

要将服务注入到异步配置中，该服务或提供者必须为

1）通过模块导入在模块范围内 2）通过全局模块提供的全局服务

在这种情况下，EndpointsService属于AppModule，但是AppModule并未导入MongooseModule进行配置（这很令人困惑，因为主要的循环依赖）。相反，您应该做的是创建一个EndpointsModule的{{1}}和provides的{{1}}，如下所示：

exports

现在，在您的EndpointsService中，您可以像这样进行异步配置

@Module({
  providers: [EndpointsService],
  exports: [EndpointsService],
})
export class EndpointsModule

MongooseModule.forRootAsync-无法解决依赖关系

1 个答案: