具有自定义 HTTP 和 ConfigService 循环依赖的 DI

问题描述

我正在尝试实现一个 ConfigService 来为项目中的正确环境检索正确的配置.我目前遇到循环依赖

I'm trying to implement a ConfigService to retrieve the right configuration for the right environment in the project. I'm currently encountering a cyclic dependancy

(index):28 Error: (SystemJS) Provider parse errors:
    Cannot instantiate cyclic dependency! Http: in NgModule AppModule
    Error: Provider parse errors:

我已经研究了代码，我认为存在问题:

I've explored the code and there is the problem, in my opinion:

自定义Http

constructor(backend: XHRBackend, options: RequestOptions, public spinnerService: SpinnerService, public exceptionService: ExceptionService, public configService: ConfigService)

异常服务

constructor(private _notificationService: NotificationService, private _spinnerService: SpinnerService, private _configService: ConfigService, private _router: Router)

配置服务

constructor(private http: Http) {}

如您所见，我在此图中说明了一个循环依赖项(没有任何好的约定):

As you can see, I've a cyclic dependancies illustrated in this diagram (without any good convention):

我现在的问题是，如何解决?我听说过 Injector，但我不确定我是否真的可以在这种情况下使用它.

My question now is, how to fix it? I've heard of Injector but I'm not sure I can really use it in this context.

预先感谢您的回答.

推荐答案

DI 无法解决循环依赖.一种解决方法是注入注入器并强制获取实例:

DI can't resolve cyclic dependencies. A workaround is to inject the injector and acquire the instance imperatively:

@Injectable()
class ConfigService {
  private http: Http;
  constructor(injector:Injector) {
    setTimeout(() => this.http = injector.get(Http);
  }
}

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