Question

我必须解决异步调用的问题。场景：
makeReservation方法返回Observable<SaveResponse>。当调用者调用makeReservation方法时应该执行 1）调用send3DRequest并订阅它并等待success事件 2）在success事件中获取必要的详细信息并返回另一个异步方法：return this.reservationHttpService.save(X)

在我的实际实现中，我收到错误：Return statement is required for non-void return type。

private makeReservation(reservationDto: ReservationDTO): Observable<SaveResponse>{
  this.reservationHttpService.send3DRequest(reservationDto.threeDQueryDetails)
    .subscribe(
      successResponse => {
        if(successResponse.enrolled === 'Y'){
          reservationDto.transRef = successResponse.transactionRef;
          reservationDto.acsUrl = successResponse.acsUrl;
          reservationDto.paReq = successResponse.paReq;

          return this.reservationHttpService.save(reservationDto);
        }
        else {
          reservationDto.transRef = successResponse.transactionRef;

          return this.reservationHttpService.save(reservationDto);
        }           
      },
      error => { throw new Error(error); });
}

-

然后，我尝试进行此更改（问题在代码中描述）：

private makeReservation(reservationDto: ReservationDTO): Observable<SaveResponse>{

  let saveResponse = new Observable<SaveResponse>(); //added change

  this.reservationHttpService.send3DRequest(reservationDto.threeDQueryDetails)
    .subscribe(
      successResponse => {
        if(successResponse.enrolled === 'Y'){
          reservationDto.transRef = successResponse.transactionRef;
          reservationDto.acsUrl = successResponse.acsUrl;
          reservationDto.paReq = successResponse.paReq;

          let result = this.reservationHttpService.save(reservationDto);
          //HOW TO INSERT the result in saveResponse and notify about change ?
        }
        else {
          reservationDto.transRef = successResponse.transactionRef;
          let result = this.reservationHttpService.save(reservationDto);
          //HOW TO INSERT the result in saveResponse and notify about change ?
        }           
      },
      error => { throw new Error(error); });

     return saveResponse; //added change
}

欢迎任何想法:) 感谢。

Answer 1

如果您查看方法定义：

private makeReservation(reservationDto: ReservationDTO): Observable<SaveResponse>

您希望makeReservation方法返回Observable类型SaveResponse。但是你不会在这里归还任何东西。

您刚开始订阅reservationHttpService.send3DRequest。

你应该宁愿：

private makeReservation(reservationDto: ReservationDTO): Observable<SaveResponse>{
  return this.reservationHttpService.send3DRequest(reservationDto.threeDQueryDetails)

（注意返回）。

现在，如果我们从你的第二个例子开始（这可能是最好的主意），我会做类似的事情：

private makeReservation(reservationDto: ReservationDTO): Observable<SaveResponse>{
  return this
    .reservationHttpService
    .send3DRequest(reservationDto.threeDQueryDetails)
    .switchMap(response => {
        let result;

        if(successResponse.enrolled === 'Y') {
          reservationDto.transRef = successResponse.transactionRef;
          reservationDto.acsUrl = successResponse.acsUrl;
          reservationDto.paReq = successResponse.paReq;

          result = this.reservationHttpService.save(reservationDto);
        }

        else {
          reservationDto.transRef = successResponse.transactionRef;
          result = this.reservationHttpService.save(reservationDto);
        }

        return Observable.of(result);
      }
    )
    .catch(err => {
      // handle your error here
      return Observable.of({});
    })
}

并且在致电时忘记在makeReservation订阅：

this.makeReservation(your_argument).subscribe();

angular2 Observable：如何等待异步结果并返回另一个异步方法

1 个答案: