Question

我在Angular 5中拥有自定义服务RequestsMethods：

@Injectable()
export class RequestsMethods {
  constructor(private http: HttpService) {
  }
}

HttpService在哪里：

import {Headers, Http, Request, RequestOptions, RequestOptionsArgs, Response, XHRBackend} from '@angular/http';
@Injectable()
export class HttpService extends Http {

constructor(private router: Router, backend: XHRBackend, options: RequestOptions) {
        super(backend, options);
    }
}

我的ngModule是：

providers: [
    BrowserXhr,
    XHRBackend,
    RequestsMethods,
    FormRegister
  ],

我收到以下错误：

错误错误：StaticInjectorError（AppModule）[RequestsMethods-> HttpService]：StaticInjectorError（平台：核心）[RequestsMethods -> HttpService]： NullInjectorError：没有HttpService的提供程序！在NullInjector.push ../ node_modules/@angular/core/fesm5/core.js.NullInjector.ge

从错误消息中得知，我需要在提供程序中注册HttpService，我尝试过：

providers: [
    HttpService,
    BrowserXhr,
    XHRBackend,
    RequestsMethods,
    FormRegister
  ],

现在我还有另一个错误：

ERROR Error: StaticInjectorError(AppModule)[XHRBackend -> ResponseOptions]: 
  StaticInjectorError(Platform: core)[XHRBackend -> ResponseOptions]: 
    NullInjectorError: No provider for ResponseOptions!

现在我的提供者部分是：

 providers: [
    {
      provide: RequestsMethods ,
      useFactory: RequestsMethodsFactory,
      deps: [HttpService]
    },
    FormRegister,
    ErrorWatcher,
    {
      provide: HttpService,
      useFactory: httpFactoryService,
      deps: [Router, XHRBackend, RequestOptions]
    }
  ],

我对ngModule文件的最后更改：

export function httpFactoryService(router: Router, backend: XHRBackend, options: RequestOptions) {
  return new HttpService(router, backend, options);
}

function RequestsMethodsFactory(router: Router, backend: XHRBackend, options: RequestOptions) {
  return new RequestsMethods(httpFactoryService(router, backend, options));
}

// AoT requires an exported function for factories
export function HttpLoaderFactory(http: HttpClient) {
  return new TranslateHttpLoader(http);
}

providers: [
    {
      provide: RequestsMethods ,
      useFactory: RequestsMethodsFactory,
      deps: [Router, XHRBackend, RequestOptions]
    },
    FormRegister,
    ErrorWatcher,
    {
      provide: HttpService,
      useFactory: httpFactoryService,
      deps: [Router, XHRBackend, RequestOptions]
    }
  ],

Answer 1

function RequestsMethodsFactory(HttpService) {
    return new RequestsMethods(new HttpService());
}

@NgModule({
  declarations: [
    AppComponent,
    ...
  ],
  imports: [
    BrowserModule,
    HttpModule
....
  ],
  providers: [
   {
     provide: RequestsMethods ,
     useFactory: RequestsMethodsFactory,
     deps: [HttpService]
   },
   ....
],
],
  bootstrap: [AppComponent]
})
export class AppModule { }

从文档中阅读：https://angular.io/guide/dependency-injection#factory-providers

Answer 2

您的HttpService通过构造函数注入三个主要标记。其中两个（XHRBackend和RequestOptions属于HttpModule（已从Angular 4.2中弃用-您应改用HttpClientModule中包含的类型）。另一个是Router，属于RouterModule。

为了使您的Ngmodule知道cnstructor中所需的类型和令牌，您将需要在{{RouterModule}属性中声明HttpModule和imports 1}}：

Ngmodule

如何在具有依赖项的提供者中注册服务？

2 个答案: