[英]RxJS catchError operator does not catch an error on an observable created from a Promise
[英]RxJS - Using an observable in catchError block
我有 2 个服务budgetTestService
和budgetService
,当有错误时我需要使用budgetTestService,当没有错误时我需要使用budgetService。 没有调用budgetTestService.getBudgetService()
管道中的budgetTestService.getBudgetService()
- console.log('test service complete');
不确定这是否应该如何完成它看起来像是我在嵌套并且做错了,我是否正确使用了语法?
this.budgetService.getBudgetDays(this.startDate, this.finishDate)
.pipe(
map(res => {
console.log('get budget day server mapping');
self.timelineBudgetDates = self.processDates(res);
}),
//map(res => {
// self.timelineBudgetDates = self.budgetTestService.getBudgetDates(self.startDate, self.finishDate);
//})
catchError(error => {
console.log('error code running');
console.log(error);
self.budgetTestService.getBudgetDates(self.startDate, self.finishDate)
.pipe(
map(res => {
console.log('test service complete');
console.log(res);
self.timelineBudgetDates = res;
})
);
return of('some return value, maybe null, maybe a good default');
})
)
.subscribe(res => {
console.log('Response = ', res);
//self.timelineBudgetDates = self.processDates(res);
//self.timelineBudgetDates = res;
});
budgetTestService
:
getBudgetDates(startDate: string, endDate: string): Observable<BudgetDate[]> {
console.log('getting budget dates from test service');
let dates = this.datesOfRange(moment(startDate), moment(endDate));
//console.log('dates:', dates);
let budgetDates: BudgetDate[] = [
new BudgetDate({ moment: moment().subtract(1, 'd').startOf('d'), earned: 100, spent: 50, onServer: true }),
new BudgetDate({ moment: moment().subtract(2, 'd').startOf('d'), earned: 101, spent: 51, onServer: true }),
new BudgetDate({ moment: moment().subtract(3, 'd').startOf('d'), earned: 102, spent: 52, onServer: true }),
new BudgetDate({ moment: moment().subtract(4, 'd').startOf('d'), earned: 103, spent: 53, onServer: true })
];
const mockResults = function(observer: Observer<BudgetDate[]>) {
observer.next(budgetDates);
observer.error('...');
observer.complete;
};
const update = new Observable(mockResults).pipe(
catchError((error: any) => Observable.throw(error))
);
return update;
}
输出:不包括: test service complete
error code running
HttpErrorResponse {headers: HttpHeaders, status: 0, statusText: "Unknown Error", url: null, ok: false, …}
getting budget dates from test service
Response = some return value, maybe null, maybe a good default
RxJS 可观察链只有在订阅时才会执行。 因此,不包括test service complete
输出背后的问题是您从未订阅测试服务调用。 特别的问题在这里:
catchError(error => {
self.budgetTestService.getBudgetDates(self.startDate, self.finishDate)
.pipe(
// ...
);
// RETURNING OTHER OBSERVABLE HERE
return of('some return value, maybe null, maybe a good default');
})
// ...
.subscribe(console.log)
在这里您调用budgetTestService
,但它的 Observable 从未被订阅。 比较一下:
catchError(error => {
return self.budgetTestService.getBudgetDates(self.startDate, self.finishDate)
.pipe(
// ...
);
})
// ...
.subscribe(console.log)
在后面的代码示例中,我们从budgetTestService
返回observable,它将成为订阅链的一部分。
在这里检查这个小例子来比较: “RxJS 中的异步错误处理程序”
希望这可以帮助
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