具有自定义HTTP和ConfigService的循环依赖的DI | 具有自定义HTTP和ConfigService的循环依赖的DI

本文介绍了具有自定义HTTP和ConfigService的循环依赖的DI的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我正在尝试实现ConfigService来检索项目中正确环境的正确配置.我目前遇到周期性依赖

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:

我已经浏览了代码，并认为存在问题:

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

CustomHttp

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

ExceptionService

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

ConfigService

constructor(private http: Http) {}

如您所见，此图中显示了周期性依赖关系(没有任何良好约定):

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，但不确定在这种情况下是否真的可以使用它.

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无法解析循环依赖性.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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