RxJS catchError

通過(guò)返回新的可觀察對(duì)象或引發(fā)錯(cuò)誤，在可觀察對(duì)象上捕獲錯(cuò)誤。

catchError<T, O extends ObservableInput<any>>(selector: (err: any, caught: Observable<T>) => O): OperatorFunction<T, T | ObservedValueOf<O>>

參量

returns

OperatorFunction<T, T | ObservedValueOf<O>>：可觀察到的事物，其來(lái)源或來(lái)源是 捕獲 selector功能。

描述

例子

發(fā)生錯(cuò)誤時(shí)繼續(xù)使用其他 Observable

import { of } from 'rxjs';
import { map, catchError } from 'rxjs/operators';


of(1, 2, 3, 4, 5).pipe(
    map(n => {
       if (n === 4) {
           throw 'four!';
      }
     return n;
    }),
    catchError(err => of('I', 'II', 'III', 'IV', 'V')),
  )
  .subscribe(x => console.log(x));
  // 1, 2, 3, I, II, III, IV, V

重傳捕獲的源，如果出現(xiàn)錯(cuò)誤，則再次可觀察，類似于 retry（）運(yùn)算符

import { of } from 'rxjs';
import { map, catchError, take } from 'rxjs/operators';


of(1, 2, 3, 4, 5).pipe(
    map(n => {
       if (n === 4) {
         throw 'four!';
      }
         return n;
    }),
    catchError((err, caught) => caught),
    take(30),
  )
  .subscribe(x => console.log(x));
  // 1, 2, 3, 1, 2, 3, ...

當(dāng)源 Observable 引發(fā)錯(cuò)誤時(shí)引發(fā)新錯(cuò)誤

import { of } from 'rxjs';
import { map, catchError } from 'rxjs/operators';


of(1, 2, 3, 4, 5).pipe(
    map(n => {
      if (n === 4) {
        throw 'four!';
      }
      return n;
    }),
    catchError(err => {
      throw 'error in source. Details: ' + err;
    }),
  )
  .subscribe(
    x => console.log(x),
    err => console.log(err)
  );
  // 1, 2, 3, error in source. Details: four!