rxjs的map和switchMap在SAP Spartacus

Type Observable<Observable<OrderEntry>> is not assignable to type Observable<number>.

看这行代码：

quantity$: Observable<number> = this.product$.pipe(map(product => this.cartService.getEntry(product.code));

返回的参数类型是：Observable<Observable<OrderEntry>>

使用switchMap就可以将嵌套的Observable打平。