从 catchError 中的 return observable 获取值

Question

budgetTestService.getBudgetDates returns an observable, how can I get the BudgetDate[] value from it in catchError?

this.budgetService.getBudgetDays(this.startDate, this.finishDate)
  .pipe(
    catchError(error => {
      self.timelineBudgetDates = self.budgetTestService.getBudgetDates(self.startDate, self.finishDate);
        return of('some return value');
      }
    )
  )
  .subscribe(res => {
    self.timelineBudgetDates = self.processDates(res);          
  });

Error:

Type 'Observable<BudgetDate[]>' is missing the following properties from type 'BudgetDate[]': length, pop, push, concat, and 25 more.

Answer 1

You can make use of Higher order function to pass this reference to catch

const errorHandler=(self)=>error => {
              self.timelineBudgetDates = 
              self.budgetTestService.getBudgetDates(self.startDate, self.finishDate);
              return of('some return value');
            }
          )

this.budgetService.getBudgetDays(this.startDate, this.finishDate)
        .pipe(
          catchError(errorHandle(this))
        )
        .subscribe(res => {
          self.timelineBudgetDates = self.processDates(res);

        });

Answer 2

If you are calling the budgetService from a component, you should be able to map the response without the need to subscribe. catchError is only execututed when the service throws an error. Please see code below...

    this.budgetService.getBudgetDays(this.startDate, this.finishDate)
        .pipe(
          map(res => { self.timelineBudgetDates = self.processDates(res); }), 
          catchError(error => {
              // handle error
            })
         );