如何處理嵌套的觀察對象

Question

這段代碼適用於我，但是想知道這是否是處理嵌套訂閱的更好方法。獲取一個數組，我需要循環並在另一個http調用中使用。這是否有效？

this.storeService.fetchStores(this.currentCoordinates).subscribe(nearestStores => { 
      nearestStores.forEach(store => { 
       this.stockService.fetchStockResults(ean, store.id).subscribe(stock => { 
        this.stockResults.push({ 
         storeObject: store, 
         ean: stock.ean, 
         ranged: stock.ranged, 
         inStock: stock.quantity > 0 ? true : false 
        } 
        ); 
       }); 
      }); 
     }); 

Answer 1

最好不要在.subscribe()中執行異步操作，這可能也會導致錯誤。您可以更好地有這些要求嵌入到的Rx流，所以你可以做錯誤處理之類的東西併發控制：

this.storeService.fetchStores(this.currentCoordinates) 
    .mergeMap(_ => _) /* emit all values from the stores array as separate values in the rx stream */ 
    .mergeMap(
    store => this.stockService.fetchStockResults(store.ean, store.id)) 
     .catch(err => Rx.Observable.of({ ean: -1, range: false, quantity: -1})), 
    (store, stock) => ({ 
         storeObject: store, 
         ean: stock.ean, 
         ranged: stock.ranged, 
         inStock: stock.quantity > 0 ? true : false 
        }), 
    10 /* concurrency; how many in-flight requests do you want?*/ 
) 
    .toArray() 
    .subscribe(stockResults => console.log(stockResults));