新建subject用来通知某事件完成

mapReady: Subject<never> = new Subject();
// 发射消息
this.mapReady.pipe(
    switchMap((_) => {
        return this.store.pipe(
    filter(store => store.workspace.pageState.stage === Stage.Third),
    select(store => store.workspace.baseData.present.content.bankSiteList.entities),
);
 // 地图加载完成后触发操作
onMapReady(map: MapClass) {
  const self = this;
  this.map = map;
  this.mapReady.next();
}
 // todo
 this.mapReady.unsubscribe();