方法内部调用的服务出错

Question

getSiteNameByMacId（）{     this.EnabledSites = [];

var macId = sessionStorage.getItem('macId');
this.dataService.getSiteNameByMacIds(macId).subscribe(data => {

  this.EnabledSites = data;

  if (this.EnabledSites.length == 1) {
    sessionStorage.setItem('siteName', this.EnabledSites[0].SiteName);
    this.route.navigate(['/type']);
  }
  if (this.EnabledSites.length == 0) {
    this.errormsg = "This PSA is not configured, please contact technical admin";
  }

});

}

it（'应该调用Login Service的isUserAuthenticated方法'，（）=> {     const spy = spyOn（service，'getSiteNameByMacIds'）。and.returnValue（Observable.empty（））;     component.getSiteNameByMacId（）;     Expect（spy）.toHaveBeenCalled（）;   }）;

TypeError：无法读取未定义的属性'getSiteNameByMacIds' TypeError：无法读取未定义的属性“ getSiteNameByMacIds”     在SiteComponent.getSiteNameByMacIds [作为getSiteNameByMacId]（http://localhost:9876/_karma_webpack_/webpack:/src/app/site/site.component.ts:20:26）     在SiteComponent.getSiteNameByMacId [作为ngOnInit]（http://localhost:9876/_karma_webpack_/webpack:/src/app/site/site.component.ts:12:14）     在UserContext上。 （http://localhost:9876/_karma_webpack_/webpack:/src/app/site/site.component.spec.ts:87:15）