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  1. import { Observable } from '../Observable';
  2. import { Subscriber } from '../Subscriber';
  3. import { ObservableInput, OperatorFunction, ObservedValueOf } from '../types';
  4. import { map } from './map';
  5. import { innerFrom } from '../observable/innerFrom';
  6. import { operate } from '../util/lift';
  7. import { createOperatorSubscriber } from './OperatorSubscriber';
  8. /* tslint:disable:max-line-length */
  9. export function exhaustMap<T, O extends ObservableInput<any>>(
  10. project: (value: T, index: number) => O
  11. ): OperatorFunction<T, ObservedValueOf<O>>;
  12. /** @deprecated The `resultSelector` parameter will be removed in v8. Use an inner `map` instead. Details: https://rxjs.dev/deprecations/resultSelector */
  13. export function exhaustMap<T, O extends ObservableInput<any>>(
  14. project: (value: T, index: number) => O,
  15. resultSelector: undefined
  16. ): OperatorFunction<T, ObservedValueOf<O>>;
  17. /** @deprecated The `resultSelector` parameter will be removed in v8. Use an inner `map` instead. Details: https://rxjs.dev/deprecations/resultSelector */
  18. export function exhaustMap<T, I, R>(
  19. project: (value: T, index: number) => ObservableInput<I>,
  20. resultSelector: (outerValue: T, innerValue: I, outerIndex: number, innerIndex: number) => R
  21. ): OperatorFunction<T, R>;
  22. /* tslint:enable:max-line-length */
  23. /**
  24. * Projects each source value to an Observable which is merged in the output
  25. * Observable only if the previous projected Observable has completed.
  26. *
  27. * <span class="informal">Maps each value to an Observable, then flattens all of
  28. * these inner Observables using {@link exhaustAll}.</span>
  29. *
  30. * ![](exhaustMap.png)
  31. *
  32. * Returns an Observable that emits items based on applying a function that you
  33. * supply to each item emitted by the source Observable, where that function
  34. * returns an (so-called "inner") Observable. When it projects a source value to
  35. * an Observable, the output Observable begins emitting the items emitted by
  36. * that projected Observable. However, `exhaustMap` ignores every new projected
  37. * Observable if the previous projected Observable has not yet completed. Once
  38. * that one completes, it will accept and flatten the next projected Observable
  39. * and repeat this process.
  40. *
  41. * ## Example
  42. *
  43. * Run a finite timer for each click, only if there is no currently active timer
  44. *
  45. * ```ts
  46. * import { fromEvent, exhaustMap, interval, take } from 'rxjs';
  47. *
  48. * const clicks = fromEvent(document, 'click');
  49. * const result = clicks.pipe(
  50. * exhaustMap(() => interval(1000).pipe(take(5)))
  51. * );
  52. * result.subscribe(x => console.log(x));
  53. * ```
  54. *
  55. * @see {@link concatMap}
  56. * @see {@link exhaust}
  57. * @see {@link mergeMap}
  58. * @see {@link switchMap}
  59. *
  60. * @param project A function that, when applied to an item emitted by the source
  61. * Observable, returns an Observable.
  62. * @return A function that returns an Observable containing projected
  63. * Observables of each item of the source, ignoring projected Observables that
  64. * start before their preceding Observable has completed.
  65. */
  66. export function exhaustMap<T, R, O extends ObservableInput<any>>(
  67. project: (value: T, index: number) => O,
  68. resultSelector?: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R
  69. ): OperatorFunction<T, ObservedValueOf<O> | R> {
  70. if (resultSelector) {
  71. // DEPRECATED PATH
  72. return (source: Observable<T>) =>
  73. source.pipe(exhaustMap((a, i) => innerFrom(project(a, i)).pipe(map((b: any, ii: any) => resultSelector(a, b, i, ii)))));
  74. }
  75. return operate((source, subscriber) => {
  76. let index = 0;
  77. let innerSub: Subscriber<T> | null = null;
  78. let isComplete = false;
  79. source.subscribe(
  80. createOperatorSubscriber(
  81. subscriber,
  82. (outerValue) => {
  83. if (!innerSub) {
  84. innerSub = createOperatorSubscriber(subscriber, undefined, () => {
  85. innerSub = null;
  86. isComplete && subscriber.complete();
  87. });
  88. innerFrom(project(outerValue, index++)).subscribe(innerSub);
  89. }
  90. },
  91. () => {
  92. isComplete = true;
  93. !innerSub && subscriber.complete();
  94. }
  95. )
  96. );
  97. });
  98. }