RxJS catchError

通过返回新的可观察对象或引发错误，在可观察对象上捕获错误。

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

参量

returns

OperatorFunction<T, T | ObservedValueOf<O>>：可观察到的事物，其来源或来源是 捕获 selector功能。

描述

例子

发生错误时继续使用其他 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

重传捕获的源，如果出现错误，则再次可观察，类似于 retry（）运算符

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, ...

当源 Observable 引发错误时引发新错误

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!