65 lines
2.9 KiB
JavaScript
65 lines
2.9 KiB
JavaScript
import { mergeMap } from './mergeMap';
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/* tslint:enable:max-line-length */
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/**
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* Projects each source value to an Observable which is merged in the output
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* Observable, in a serialized fashion waiting for each one to complete before
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* merging the next.
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*
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* <span class="informal">Maps each value to an Observable, then flattens all of
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* these inner Observables using {@link concatAll}.</span>
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*
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* <img src="./img/concatMap.png" width="100%">
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*
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* Returns an Observable that emits items based on applying a function that you
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* supply to each item emitted by the source Observable, where that function
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* returns an (so-called "inner") Observable. Each new inner Observable is
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* concatenated with the previous inner Observable.
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*
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* __Warning:__ if source values arrive endlessly and faster than their
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* corresponding inner Observables can complete, it will result in memory issues
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* as inner Observables amass in an unbounded buffer waiting for their turn to
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* be subscribed to.
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*
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* Note: `concatMap` is equivalent to `mergeMap` with concurrency parameter set
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* to `1`.
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*
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* @example <caption>For each click event, tick every second from 0 to 3, with no concurrency</caption>
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* var clicks = Rx.Observable.fromEvent(document, 'click');
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* var result = clicks.concatMap(ev => Rx.Observable.interval(1000).take(4));
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* result.subscribe(x => console.log(x));
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*
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* // Results in the following:
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* // (results are not concurrent)
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* // For every click on the "document" it will emit values 0 to 3 spaced
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* // on a 1000ms interval
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* // one click = 1000ms-> 0 -1000ms-> 1 -1000ms-> 2 -1000ms-> 3
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*
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* @see {@link concat}
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* @see {@link concatAll}
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* @see {@link concatMapTo}
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* @see {@link exhaustMap}
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* @see {@link mergeMap}
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* @see {@link switchMap}
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*
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* @param {function(value: T, ?index: number): ObservableInput} project A function
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* that, when applied to an item emitted by the source Observable, returns an
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* Observable.
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* @param {function(outerValue: T, innerValue: I, outerIndex: number, innerIndex: number): any} [resultSelector]
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* A function to produce the value on the output Observable based on the values
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* and the indices of the source (outer) emission and the inner Observable
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* emission. The arguments passed to this function are:
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* - `outerValue`: the value that came from the source
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* - `innerValue`: the value that came from the projected Observable
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* - `outerIndex`: the "index" of the value that came from the source
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* - `innerIndex`: the "index" of the value from the projected Observable
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* @return {Observable} An Observable that emits the result of applying the
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* projection function (and the optional `resultSelector`) to each item emitted
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* by the source Observable and taking values from each projected inner
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* Observable sequentially.
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* @method concatMap
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* @owner Observable
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*/
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export function concatMap(project, resultSelector) {
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return mergeMap(project, resultSelector, 1);
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}
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//# sourceMappingURL=concatMap.js.map
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