Angular 9/rxjs: 如何处理switchMap内部抛出的错误？

Question

我正在使用 Angular (9) powered Bootstrap (6.1.0) TypeAhead 并像这样定义其搜索功能：

search = (text$: Observable<string>) => {
    return text$.pipe(
      debounceTime(200),
      distinctUntilChanged(),
      // switchMap allows returning an observable rather than maps array
      switchMap((searchText) => {
        if (!searchText || searchText.trim().length == 0) {
          // when the user erases the searchText
          this.dealerRepUserID = 0;
          this.dealerRepChanging.emit(this.dealerRepUserID);
          return EMPTY;
        }
        else if (this.dealerID == this.hostOrganizationID) {
          // get a list of host reps
          return this.myService.getHostRepsAutoComplete(searchText, this.includeInactive);
        } else {
          // get a list of dealer reps
          return this.myService.getDealerReps(this.dealerID, searchText);
        }
      })
    );
  }

该函数必须 return 一个 Observable。如何捕获 switchMap 中抛出的错误？

Answer 1

你试过catchError

import { catchError } from 'rxjs/operators';

return text$.pipe(
      debounceTime(200),
      distinctUntilChanged(),
      // switchMap allows returning an observable rather than maps array
      switchMap((searchText) => {
        if (!searchText || searchText.trim().length == 0) {
          // when the user erases the searchText
          this.dealerRepUserID = 0;
          this.dealerRepChanging.emit(this.dealerRepUserID);
          return EMPTY;
        }
        else if (this.dealerID == this.hostOrganizationID) {
          // get a list of host reps
          return this.myService.getHostRepsAutoComplete(searchText, this.includeInactive).pipe(catchError(error => of());
        } else {
          // get a list of dealer reps
          return this.myService.getDealerReps(this.dealerID, searchText).pipe(catchError(error => of());
        }
      })
    );

这是我的应用效果

public loadDataPerformance$: Observable<Action> = createEffect(() => {
    return this.actions$.pipe(
      ofType(RiskProfileActions.loadDataPerformance),
      withLatestFrom(
        this.store$.select(fromRoot.getAnalyticsFilterSelectedOptions),
        this.store$.pipe(select(fromFactoryPerformance.getFactoryId))
      ),
      switchMap(([{ recordDate }, filters, factoryId]) =>
        this.riskProfileApiService.getDataPerformanceData(filters, factoryId, recordDate).pipe(
          map((riskDataPerformanceData: PerformanceDataModel) =>
            RiskProfileActions.loadRiskScoreBreakdownPerformanceSuccess(riskDataPerformanceData)
          ),
          catchError(error => of(RiskProfileActions.loadRiskScoreBreakdownPerformanceFail(error)))
        )
      )
    );
  });

Answer 2

switchMap 本身不会抛出任何错误，可能会做一些意想不到的事情是返回的观察值 this.myService.getHostRepsAutoComplete 和 this.myService.getDealerReps。捕获错误的一个棘手时刻是，只要有 error 抛出错误的可观察对象就会被杀死。

例如

observable$.pipe(
 switchMap(() => observable2$),
 catchError(() => doSomethingFunction())
).subscribe()

observable$一旦出现错误就会完成，这将完成您的搜索流，错误后您将不会再获得任何数据。

正如 Phat Tran Ky 在他的示例中所展示的那样，错误处理应该发生在 switchMap 运算符

中的新流中

observable$.pipe(
 switchMap(() => observable2$.pipe(catchError(() => doSomethingFunction())),
 )
).subscribe()

只要从内部抛出错误，这样做就会终止内部可观察对象 (observable2$)，但不会终止外部可观察对象的外部订阅 observable$

为了在一处处理错误，您可以做的进一步改进可能是将内部可观察对象合并为一个，例如，类似

observable$.pipe(
 switchMap(() => {
   return merge(
   observable1$.pipe(filter(() => ${your if else condition for case 1})),
   observable2$.pipe(filter(() => ${your if else condition for case 2})),
   observable3$.pipe(filter(() => ${your if else condition for case 3})),
   ).pipe(catchError((error) => yourErrorHandlerFunction(error)))
  })),
 )
).subscribe()

Angular 9/rxjs: 如何处理switchMap内部抛出的错误？

Angular 9/rxjs: How to handle an error thrown inside switchMap?

rxjs

angular9

switchmap