问Promise.all类型脚本不进行异步调用

EN

if(this.selectedDomains.length > 0) {
      for(let i=0; i<this.selectedDomains.length; i++){
        promises.push(

          this.policyService.exportPolicies(this.selectedDomains[i].id, this.config['data'].policies)


        );

      }

      //wait for all exportPolicies calls to finish
      Promise.all(promises).then(function () {
        console.log("ALL resolved !!");
          let successMsg = this.translate.instant("policy.resources.export_policy_success",
            [this.config['data'].policies.length, this.selectedDomains.length]);
          this.messageHelperService.showSuccess({hide: true, message: successMsg});
        }
      ).catch(function () {
      });
    }

export class PolicyService {

  constructor ( private baseService : BaseService ) {
  }
  exportPolicies(domainId, policyIds) : Observable<import("@angular/common/http").HttpEvent<any[]>>{
    let url = COMMON.LEGACY_API_PATH + `policy/exportPolicy/${domainId}`;
    return this.baseService.postData(url, policyIds);
  }

export declare class BaseService {
    private http;
    constructor(http: HttpClient);
    handleError<T>(operation?: string, result?: T): (error: any) => Observable<T>;
    log(message: string, response: object): void;
    deleteData(url: string, data?: any): Observable<import("@angular/common/http").HttpEvent<any[]>>;
    getData(url: string): Observable<any[]>;
    postData(url: string, data?: any, params?: any): Observable<import("@angular/common/http").HttpEvent<any[]>>;
    putData(url: string, data?: any, params?: any): Observable<import("@angular/common/http").HttpEvent<any[]>>;
    patchData(url: string, data?: any, params?: any): Observable<import("@angular/common/http").HttpEvent<any[]>>;
    headData(url: string): Observable<any[]>;
    static ɵfac: ɵngcc0.ɵɵFactoryDef<BaseService, never>;
}