concatMap.ts
3.4 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
import { mergeMap } from './mergeMap';
import { ObservableInput, OperatorFunction, ObservedValueOf } from '../types';
/* tslint:disable:max-line-length */
export function concatMap<T, O extends ObservableInput<any>>(project: (value: T, index: number) => O): OperatorFunction<T, ObservedValueOf<O>>;
/** @deprecated resultSelector no longer supported, use inner map instead */
export function concatMap<T, O extends ObservableInput<any>>(project: (value: T, index: number) => O, resultSelector: undefined): OperatorFunction<T, ObservedValueOf<O>>;
/** @deprecated resultSelector no longer supported, use inner map instead */
export function concatMap<T, R, O extends ObservableInput<any>>(project: (value: T, index: number) => O, resultSelector: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R): OperatorFunction<T, R>;
/* tslint:enable:max-line-length */
/**
* Projects each source value to an Observable which is merged in the output
* Observable, in a serialized fashion waiting for each one to complete before
* merging the next.
*
* <span class="informal">Maps each value to an Observable, then flattens all of
* these inner Observables using {@link concatAll}.</span>
*
* 
*
* Returns an Observable that emits items based on applying a function that you
* supply to each item emitted by the source Observable, where that function
* returns an (so-called "inner") Observable. Each new inner Observable is
* concatenated with the previous inner Observable.
*
* __Warning:__ if source values arrive endlessly and faster than their
* corresponding inner Observables can complete, it will result in memory issues
* as inner Observables amass in an unbounded buffer waiting for their turn to
* be subscribed to.
*
* Note: `concatMap` is equivalent to `mergeMap` with concurrency parameter set
* to `1`.
*
* ## Example
* For each click event, tick every second from 0 to 3, with no concurrency
*
* ```ts
* import { fromEvent, interval } from 'rxjs';
* import { concatMap, take } from 'rxjs/operators';
*
* const clicks = fromEvent(document, 'click');
* const result = clicks.pipe(
* concatMap(ev => interval(1000).pipe(take(4)))
* );
* result.subscribe(x => console.log(x));
*
* // Results in the following:
* // (results are not concurrent)
* // For every click on the "document" it will emit values 0 to 3 spaced
* // on a 1000ms interval
* // one click = 1000ms-> 0 -1000ms-> 1 -1000ms-> 2 -1000ms-> 3
* ```
*
* @see {@link concat}
* @see {@link concatAll}
* @see {@link concatMapTo}
* @see {@link exhaustMap}
* @see {@link mergeMap}
* @see {@link switchMap}
*
* @param {function(value: T, ?index: number): ObservableInput} project A function
* that, when applied to an item emitted by the source Observable, returns an
* Observable.
* @return {Observable} An Observable that emits the result of applying the
* projection function (and the optional deprecated `resultSelector`) to each item emitted
* by the source Observable and taking values from each projected inner
* Observable sequentially.
* @method concatMap
* @owner Observable
*/
export function concatMap<T, R, O extends ObservableInput<any>>(
project: (value: T, index: number) => O,
resultSelector?: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R
): OperatorFunction<T, ObservedValueOf<O>|R> {
return mergeMap(project, resultSelector, 1);
}