Question

我正在尝试获取最后发布的3个值，代码如下：我希望在填充uiOrder并调用cancelOrderItem（）几次后，我可以使用getHistory（）访问订单的最后3个版本，但是我实际上得到了最后（当前）值3次，我尝试了重播主题（3）与相同的结果。这是我的代码：

export class OrdersService {

  public readonly orders: Observable<Order[]>;
  public readonly uiOrder: Observable<Order>;

  private _orders: BehaviorSubject<Order[]>;
  private _uiOrder: BehaviorSubject<Order>;

  private dataStore: {
    uiOrder: Order,
    orders: Order[]
 };


  constructor() {

    this.dataStore = {
      uiOrder: null,
      orders: []
    };

    this._orders = <BehaviorSubject<Order[]>>new BehaviorSubject([]);
    this._uiOrder = <BehaviorSubject<Order>>new BehaviorSubject({});
    this.orders = this._orders.asObservable();
    this.uiOrder = this._uiOrder.asObservable();
  }

  getOrder(orderId: number | string) {
    for (let i = 0; i < this.dataStore.orders.length; i++) {
      if (this.dataStore.orders[i].id == orderId) {
        this.dataStore.orders[i].lastAccess = moment().format().slice(0, 19) + 'Z';
        this.dataStore.uiOrder = this.dataStore.orders[i];
        this.updateUiOrder();
      }
    }
  }


  cancelOrderItem(action) {
    this.dataStore.uiOrder.sections[action.sectionIndex].orderDetails.splice(action.orderDetailsIndex, 1);
    this.updateUiOrder()
  }

  getHistory() {
    this.uiOrder.take(3).subscribe((res) => {
      console.log('uiOrder', res);
    }).unsubscribe()
  }

  updateUiOrder() {
    console.log('updating ui order');
    this._uiOrder.next(this.dataStore.uiOrder);
  }

}

我做错了什么？

Answer 1

您要查找的运算符是bufferCount(3,1)，它会创建最后3个值的滑动窗口。缺点：它只会在累积3个值后开始发射。如果你想拥有第一个值，你可以这样做：

Rx.Observable.from([null,null])
  .concat(this.uiOrder)
  .bufferCount(3,1)
  .subscribe(uiOrderHistory => ... );

这样你的大理石图将如下所示：

---Order1-----------------Order2--------------------Order3
bufferCount(3,1)
---[null,null,Order1]-----[null,Order1,Order2]------[Order1,Order2,Order3]

Answer 2

你可能会过度思考它。如果您需要随时提供最新的3个订单，为什么不将它们存储在每次// fld seems to be the class of the input field but looking at all input elements should work too List<WebElement> inputs = driver.findElements(By.className("fld")); for (WebElement input: inputs) { if (inputs.getAttribute("placeholder") == "Email or username") { // ... } }发出新订单时都会更新的数组中？

uiOrder

现在，只要您想知道最近的3个订单，只需查看orderHistory:Order[] = []; orders$ = this.uiOrder.subscribe(order => let h = this.orderHistory; //add the order to history array: h = [...h, order]; //splice the array to keep only the last 3 orders: if (h.length > 3) h.splice(0,h.length-3) );即可。作为奖励，该查找是同步操作。

Answer 3

getHistory() {
this.uiOrder.takeLast(3).subscribe((res) => {
  console.log('uiOrder', res);
}).unsubscribe()  }

takeLast运算符检索从源可观察对象发出的最后三个值。

Rx.js无法超越值

3 个答案: