61 lines
1.7 KiB
Plaintext
61 lines
1.7 KiB
Plaintext
import { EmptyError } from '../util/EmptyError';
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import { MonoTypeOperatorFunction } from '../types';
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import { operate } from '../util/lift';
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import { createOperatorSubscriber } from './OperatorSubscriber';
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/**
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* If the source observable completes without emitting a value, it will emit
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* an error. The error will be created at that time by the optional
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* `errorFactory` argument, otherwise, the error will be {@link EmptyError}.
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*
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* 
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*
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* ## Example
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*
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* Throw an error if the document wasn't clicked within 1 second
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*
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* ```ts
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* import { fromEvent, takeUntil, timer, throwIfEmpty } from 'rxjs';
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*
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* const click$ = fromEvent(document, 'click');
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*
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* click$.pipe(
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* takeUntil(timer(1000)),
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* throwIfEmpty(() => new Error('The document was not clicked within 1 second'))
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* )
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* .subscribe({
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* next() {
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* console.log('The document was clicked');
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* },
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* error(err) {
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* console.error(err.message);
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* }
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* });
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* ```
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*
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* @param errorFactory A factory function called to produce the
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* error to be thrown when the source observable completes without emitting a
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* value.
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* @return A function that returns an Observable that throws an error if the
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* source Observable completed without emitting.
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*/
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export function throwIfEmpty<T>(errorFactory: () => any = defaultErrorFactory): MonoTypeOperatorFunction<T> {
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return operate((source, subscriber) => {
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let hasValue = false;
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source.subscribe(
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createOperatorSubscriber(
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subscriber,
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(value) => {
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hasValue = true;
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subscriber.next(value);
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},
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() => (hasValue ? subscriber.complete() : subscriber.error(errorFactory()))
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)
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);
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});
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}
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function defaultErrorFactory() {
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return new EmptyError();
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}
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