有人知道是否有机会从商店获得价值，然后致电Angular HTTP服务？请参见下面的示例。提前致谢。

我有一个使用异步方法的服务。在此方法中，我调用Angular HTTP服务，但是在调用Angular HTTP服务之前，我想从商店（Oauth访问令牌）检索一些值。问题是我将Oauth令牌存储在商店中，我必须将令牌添加到请求中。如果服务器响应401错误，则我刷新令牌并重复请求或新令牌请求。

@Injectable()export class Interceptor {   public get(request: Request): Observable<any> {      return this.store.select((s) => s.session.accessToken)         // tried .switchMap, it wasn't working for multiple requests         // .flatMap also is not working         // commented below is working but I don't think that it is right solution         // return Observable.of(request)         // .withLatestFrom(this.store.select((s) => {         //    return s.session.accessToken         // }))         // .flatMap(([config, accessToken]) => { ... })         .flatMap((accessToken) => {            request.headers.set("Authorization", `Bearer ${accessToken}`);            return this.http.request(request);         })         .map((response) => {            return response.json();         })         .catch((response) => {            return this.handleError(response, request);         });   }   // handle errors   private handleError(response: Response, request: Request): Observable<Response> {       // handle outdated api tokens       if (response.status === HttpStatusesEnum.Unauthorized) {           const deferredRequest = new DeferredRequestModel({ request });           // appends HTTP request configuration object with deferred response           // attached to buffer           this.buffer(deferredRequest );           return deferredRequest.observable;       }       // handle server error       if (response.status === HttpStatusesEnum.InternalServerError) {           ...       }       ...       return Observable.throw(response);   }}export class DeferredRequestModel {    public observable: AsyncSubject<Response>;    public request: Request;    constructor(obj?: Partial<DeferredRequestModel>) {        this.observable = new AsyncSubject<Response>();        this.request = obj && obj.request || null;    }    public reject(error?: any): void {        this.end({ isValue: false, value: error });    }    public resolve(value?: any): void {        this.end({ isValue: true, value });    }    private end(result: any): void {        if (this.observable.isStopped) {            console.warn("Deferred already resloved/rejected.");            return;        }        if (result.isValue) {            this.observable.next(result.value);            this.observable.complete();        } else {            this.observable.error(result.error);        }    }}

然后，当我致电某些服务时，它将通过Interceptor发送请求。

export class SomeEffect {   constructor(private someService: SomeService) {}   @Effect()   public someMethod(): Observable<Action> {      return this.actions$.ofType(SOME_ACTION_GET)         .map((action: SomeActions.Get) => action.payload)         .switchMap((someObj) => {            // someMethod call interceptor inside someService, it won't call angular             // http service directly            return this.someService.someMethod(someObj);         })         .map((someResult) => {            return new SomeActions.GetSuccess(someResult);         });   }}

我尝试在拦截器中使用switchmap，但是如果拦截器被称为多次一次，则它将无法使用。

看答案

return this.store.select(reducers.getAccessToken)  .take(1)  .switchMap(token => {    const headers = new Headers();    headers.append('Authorization', `Bearer ${token}`);    return this.http.get('...', { headers });  });

export const getAccessToken = createSelector(  getAuthState, authReducer.getToken);