为什么rxjs没有将我的Observable.throw传递给订阅者？

时间：2017-08-04 16:09:08

标签： angular rxjs

我在服务中有以下代码，它从Http请求创建一个observable。

  const httpObservable = this.http.post(url, JSON.stringify(request))
    .map((res: Response) => res.json())
    .catch((error, caught) => {
      console.log('There was an API error for ' + url);
      console.log('Rethrowing');
      return Observable.throw(error);
    });
  return httpObservable;

指定的URL上没有可用的服务器，并且正在执行catch块。正如您所看到的，catch处理程序返回Observable.throw(error)，应该（据我所知）在下一个使用上述函数的块中捕获。

const request = new Api.ThemeInfoGetQuery();
console.log('Sending request');
this.response = this.apiService.request(Api.ThemeInfoGetQuery.url, request);
console.log('Setting catch');
this.response.catch((err: any, caught: Observable<Api.ThemeInfoGetResponse>) => {
  console.log('The rethrown error was detected');
  return Observable.throw(err);
});
this.response.subscribe(x => {
  console.log('There was no error');
});

这是我期望在控制台中看到的输出。

  1. 发送请求
  2. 设置捕获
  3. 存在API错误
  4. 重新抛出
  5. 检测到重新抛出错误

    6. 但我只是看到第4步。有人可以建议我可以尝试确保订阅者的.catch也被执行吗？

    Sending request
load-theme.resolver.ts:31 Setting catch
zone.js:2177 OPTIONS http://localhost:5000/api/theme/get-theme net::ERR_CONNECTION_REFUSED
scheduleTask @ zone.js:2177
webpackJsonp.../../../../zone.js/dist/zone.js.ZoneDelegate.scheduleTask @ zone.js:384
onScheduleTask @ zone.js:274
webpackJsonp.../../../../zone.js/dist/zone.js.ZoneDelegate.scheduleTask @ zone.js:378
webpackJsonp.../../../../zone.js/dist/zone.js.Zone.scheduleTask @ zone.js:209
webpackJsonp.../../../../zone.js/dist/zone.js.Zone.scheduleMacroTask @ zone.js:232
(anonymous) @ zone.js:2201
send @ VM5471:3
(anonymous) @ http.es5.js?9c1c:1275
webpackJsonp.../../../../rxjs/Observable.js.Observable._trySubscribe @ Observable.js:171
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:159
webpackJsonp.../../../../rxjs/operator/map.js.MapOperator.call @ map.js:54
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/do.js.DoOperator.call @ do.js?d062:63
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/delay.js.DelayOperator.call @ delay.js?1cee:63
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/catch.js.CatchOperator.call @ catch.js?0239:79
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/finally.js.FinallyOperator.call @ finally.js?667f:26
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../../src/app/tru-control/resolvers/load-theme.resolver.ts.LoadThemeResolver.resolveBrand @ load-theme.resolver.ts:37
LoadThemeResolver @ load-theme.resolver.ts:19
_createClass @ core.es5.js:9518
_createProviderInstance$1 @ core.es5.js:9486
resolveNgModuleDep @ core.es5.js:9471
webpackJsonp.../../../core/@angular/core.es5.js.NgModuleRef_.get @ core.es5.js:10557
webpackJsonp.../../../router/@angular/router.es5.js.PreActivation.getToken @ router.es5.js?1fca:4566
webpackJsonp.../../../router/@angular/router.es5.js.PreActivation.getResolver @ router.es5.js?1fca:4554
webpackJsonp.../../../router/@angular/router.es5.js.PreActivation.resolveNode @ router.es5.js?1fca:4534
webpackJsonp.../../../router/@angular/router.es5.js.PreActivation.runResolve @ router.es5.js?1fca:4515
(anonymous) @ router.es5.js?1fca:4282
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber._tryNext @ mergeMap.js?a3bf:120
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber._next @ mergeMap.js?a3bf:110
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next @ Subscriber.js:89
webpackJsonp.../../../../rxjs/observable/ArrayObservable.js.ArrayObservable._subscribe @ ArrayObservable.js:114
webpackJsonp.../../../../rxjs/Observable.js.Observable._trySubscribe @ Observable.js:171
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:159
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapOperator.call @ mergeMap.js?a3bf:85
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/reduce.js.ReduceOperator.call @ reduce.js?4c7d:74
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/map.js.MapOperator.call @ map.js:54
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
subscribeToResult @ subscribeToResult.js:22
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber._innerSub @ mergeMap.js?a3bf:130
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber._tryNext @ mergeMap.js?a3bf:127
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber._next @ mergeMap.js?a3bf:110
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next @ Subscriber.js:89
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webpackJsonp.../../../../rxjs/InnerSubscriber.js.InnerSubscriber._next @ InnerSubscriber.js:23
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next @ Subscriber.js:89
webpackJsonp.../../../../rxjs/operator/map.js.MapSubscriber._next @ map.js:83
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next @ Subscriber.js:89
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber.notifyNext @ mergeMap.js?a3bf:143
webpackJsonp.../../../../rxjs/InnerSubscriber.js.InnerSubscriber._next @ InnerSubscriber.js:23
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next @ Subscriber.js:89
webpackJsonp.../../../../rxjs/operator/every.js.EverySubscriber.notifyComplete @ every.js?5a03:53
webpackJsonp.../../../../rxjs/operator/every.js.EverySubscriber._complete @ every.js?5a03:70
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.complete @ Subscriber.js:114
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber._complete @ mergeMap.js?a3bf:135
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.complete @ Subscriber.js:114
webpackJsonp.../../../../rxjs/observable/ArrayObservable.js.ArrayObservable._subscribe @ ArrayObservable.js:116
webpackJsonp.../../../../rxjs/Observable.js.Observable._trySubscribe @ Observable.js:171
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:159
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapOperator.call @ mergeMap.js?a3bf:85
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/every.js.EveryOperator.call @ every.js?5a03:33
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
subscribeToResult @ subscribeToResult.js:22
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber._innerSub @ mergeMap.js?a3bf:130
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber._tryNext @ mergeMap.js?a3bf:127
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber._next @ mergeMap.js?a3bf:110
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next @ Subscriber.js:89
webpackJsonp.../../../../rxjs/operator/every.js.EverySubscriber.notifyComplete @ every.js?5a03:53
webpackJsonp.../../../../rxjs/operator/every.js.EverySubscriber._complete @ every.js?5a03:70
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.complete @ Subscriber.js:114
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber._complete @ mergeMap.js?a3bf:135
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.complete @ Subscriber.js:114
webpackJsonp.../../../../rxjs/observable/ArrayObservable.js.ArrayObservable._subscribe @ ArrayObservable.js:116
webpackJsonp.../../../../rxjs/Observable.js.Observable._trySubscribe @ Observable.js:171
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:159
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapOperator.call @ mergeMap.js?a3bf:85
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/every.js.EveryOperator.call @ every.js?5a03:33
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapOperator.call @ mergeMap.js?a3bf:85
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/map.js.MapOperator.call @ map.js:54
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
subscribeToResult @ subscribeToResult.js:22
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber._innerSub @ mergeMap.js?a3bf:130
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber._tryNext @ mergeMap.js?a3bf:127
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber._next @ mergeMap.js?a3bf:110
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next @ Subscriber.js:89
webpackJsonp.../../../../rxjs/operator/map.js.MapSubscriber._next @ map.js:83
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next @ Subscriber.js:89
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber.notifyNext @ mergeMap.js?a3bf:143
webpackJsonp.../../../../rxjs/InnerSubscriber.js.InnerSubscriber._next @ InnerSubscriber.js:23
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next @ Subscriber.js:89
webpackJsonp.../../../../rxjs/operator/map.js.MapSubscriber._next @ map.js:83
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next @ Subscriber.js:89
webpackJsonp.../../../../rxjs/observable/ScalarObservable.js.ScalarObservable._subscribe @ ScalarObservable.js:49
webpackJsonp.../../../../rxjs/Observable.js.Observable._trySubscribe @ Observable.js:171
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:159
webpackJsonp.../../../../rxjs/operator/map.js.MapOperator.call @ map.js:54
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
subscribeToResult @ subscribeToResult.js:22
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber._innerSub @ mergeMap.js?a3bf:130
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber._tryNext @ mergeMap.js?a3bf:127
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber._next @ mergeMap.js?a3bf:110
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next @ Subscriber.js:89
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber.notifyNext @ mergeMap.js?a3bf:143
webpackJsonp.../../../../rxjs/InnerSubscriber.js.InnerSubscriber._next @ InnerSubscriber.js:23
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next @ Subscriber.js:89
webpackJsonp.../../../../rxjs/operator/map.js.MapSubscriber._next @ map.js:83
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next @ Subscriber.js:89
webpackJsonp.../../../../rxjs/observable/ScalarObservable.js.ScalarObservable._subscribe @ ScalarObservable.js:49
webpackJsonp.../../../../rxjs/Observable.js.Observable._trySubscribe @ Observable.js:171
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:159
webpackJsonp.../../../../rxjs/operator/map.js.MapOperator.call @ map.js:54
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
subscribeToResult @ subscribeToResult.js:22
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber._innerSub @ mergeMap.js?a3bf:130
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber._tryNext @ mergeMap.js?a3bf:127
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapSubscriber._next @ mergeMap.js?a3bf:110
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next @ Subscriber.js:89
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber._next @ Subscriber.js:125
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next @ Subscriber.js:89
webpackJsonp.../../../../rxjs/operator/map.js.MapSubscriber._next @ map.js:83
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next @ Subscriber.js:89
webpackJsonp.../../../../rxjs/operator/map.js.MapSubscriber._next @ map.js:83
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next @ Subscriber.js:89
webpackJsonp.../../../../rxjs/operator/map.js.MapSubscriber._next @ map.js:83
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next @ Subscriber.js:89
webpackJsonp.../../../../rxjs/operator/last.js.LastSubscriber._complete @ last.js?576b:110
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.complete @ Subscriber.js:114
webpackJsonp.../../../../rxjs/operator/mergeAll.js.MergeAllSubscriber._complete @ mergeAll.js:94
webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.complete @ Subscriber.js:114
webpackJsonp.../../../../rxjs/observable/ScalarObservable.js.ScalarObservable._subscribe @ ScalarObservable.js:51
webpackJsonp.../../../../rxjs/Observable.js.Observable._trySubscribe @ Observable.js:171
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:159
webpackJsonp.../../../../rxjs/operator/mergeAll.js.MergeAllOperator.call @ mergeAll.js:63
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/last.js.LastOperator.call @ last.js?576b:39
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/map.js.MapOperator.call @ map.js:54
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/map.js.MapOperator.call @ map.js:54
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/map.js.MapOperator.call @ map.js:54
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/catch.js.CatchOperator.call @ catch.js?0239:79
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapOperator.call @ mergeMap.js?a3bf:85
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapOperator.call @ mergeMap.js?a3bf:85
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/map.js.MapOperator.call @ map.js:54
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapOperator.call @ mergeMap.js?a3bf:85
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapOperator.call @ mergeMap.js?a3bf:85
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/mergeMap.js.MergeMapOperator.call @ mergeMap.js?a3bf:85
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
webpackJsonp.../../../../rxjs/operator/map.js.MapOperator.call @ map.js:54
webpackJsonp.../../../../rxjs/Observable.js.Observable.subscribe @ Observable.js:156
(anonymous) @ Observable.js:203
ZoneAwarePromise @ zone.js:776
webpackJsonp.../../../../rxjs/Observable.js.Observable.forEach @ Observable.js:199
(anonymous) @ router.es5.js?1fca:4148
ZoneAwarePromise @ zone.js:776
webpackJsonp.../../../router/@angular/router.es5.js.Router.runNavigate @ router.es5.js?1fca:4073
(anonymous) @ router.es5.js?1fca:4040
webpackJsonp.../../../../zone.js/dist/zone.js.ZoneDelegate.invoke @ zone.js:365
onInvoke @ core.es5.js:3890
webpackJsonp.../../../../zone.js/dist/zone.js.ZoneDelegate.invoke @ zone.js:364
webpackJsonp.../../../../zone.js/dist/zone.js.Zone.run @ zone.js:125
(anonymous) @ zone.js:760
webpackJsonp.../../../../zone.js/dist/zone.js.ZoneDelegate.invokeTask @ zone.js:398
onInvokeTask @ core.es5.js:3881
webpackJsonp.../../../../zone.js/dist/zone.js.ZoneDelegate.invokeTask @ zone.js:397
webpackJsonp.../../../../zone.js/dist/zone.js.Zone.runTask @ zone.js:165
drainMicroTaskQueue @ zone.js:593
api.service.ts?c446:92 There was an API error for http://localhost:5000/api/theme/get-theme
api.service.ts?c446:100 Rethrowing
core.es5.js:1020 ERROR Response {_body: ProgressEvent, status: 0, ok: false, statusText: "", headers: Headers…}headers: Headersok: falsestatus: 0statusText: ""type: 3url: null_body: ProgressEventbubbles: falsecancelBubble: falsecancelable: falsecomposed: falsecurrentTarget: XMLHttpRequestdefaultPrevented: falseeventPhase: 0isTrusted: truelengthComputable: falseloaded: 0path: Array(0)returnValue: truesrcElement: XMLHttpRequesttarget: XMLHttpRequesttimeStamp: 5433.305total: 0type: "error"__proto__: ProgressEvent__proto__: Body

3 个答案:

答案 0 :(得分：1)

catch是一个RxJS运算符，因此它返回一个observable - 你忽略它。它是已应用catch的返回的observable，而不是catch被调用的可观察对象。

要使catch生效，您需要使用返回的observable，如下所示：

this.response = this.response.catch((err, caught) => {
  console.log('The rethrown error was detected');
  return Observable.throw(err);
});

答案 1 :(得分：0)

您可以在catch中抛出新错误：

.catch(err => {
    this.error = "Error: " + err.status
    throw new Error('Got a 404')
})

这会将它传递到流上，然后可以再次捕获：

.subscribe(
  result => console.log(result),
  err => {
    console.log('subscribe error')
  });

Live plunker example

您也可以Observable.throw()使用类似于问题的方式

.catch(err => {
  console.log('Error: ', err)
  return Observable.throw('new error')
})
.subscribe(
  result => console.log(result));

正如his answer中提到的@cartant：你没有使用返回的observable，另一个选项而不是将响应分配给.catch的结果是直接订阅结果，如图所示上方。

Updated plunker with both methods

答案 2 :(得分：0)

this.response.subscribe(
  x => {
    console.log('There was no error');
  }
  err => {
    console.log('There was error', err);
  }
);
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