TypeScript operators.exhaustMap函數代碼示例

> => (action$, state$, { selectLogFilterQueryAsJson, selectVisibleLogSummary }) => {
  const filterQuery$ = state$.pipe(map(selectLogFilterQueryAsJson));
  const summaryInterval$ = state$.pipe(
    map(selectVisibleLogSummary),
    map(({ start, end }) => (start && end ? getLoadParameters(start, end) : null)),
    filter(isNotNull)
  );

  const shouldLoadBetweenNewInterval$ = action$.pipe(
    filter(logPositionActions.reportVisibleSummary.match),
    filter(
      ({ payload: { bucketsOnPage, pagesBeforeStart, pagesAfterEnd } }) =>
        bucketsOnPage < MINIMUM_BUCKETS_PER_PAGE ||
        pagesBeforeStart < MINIMUM_BUFFER_PAGES ||
        pagesAfterEnd < MINIMUM_BUFFER_PAGES
    ),
    map(({ payload: { start, end } }) => getLoadParameters(start, end))
  );

  const shouldLoadWithNewFilter$ = action$.pipe(
    filter(logFilterActions.applyLogFilterQuery.match),
    withLatestFrom(filterQuery$, (filterQuery, filterQueryString) => filterQueryString)
  );

  return merge(
    shouldLoadBetweenNewInterval$.pipe(
      withLatestFrom(filterQuery$),
      exhaustMap(([{ start, end, bucketSize }, filterQuery]) => [
        loadSummary({
          start,
          end,
          sourceId: 'default',
          bucketSize,
          filterQuery,
        }),
      ])
    ),
    shouldLoadWithNewFilter$.pipe(
      withLatestFrom(summaryInterval$),
      exhaustMap(([filterQuery, { start, end, bucketSize }]) => [
        loadSummary({
          start,
          end,
          sourceId: 'default',
          bucketSize: (end - start) / LOAD_BUCKETS_PER_PAGE,
          filterQuery,
        }),
      ])
    )
  );
};

  exhaustMap2() {
    const firstInterval = interval(1000).pipe(take(10));
    const secondInterval = interval(1000).pipe(take(2));

    const exhaustSub = firstInterval
      .pipe(
        exhaustMap(f => {
          console.log(`Emission Corrected of first interval: ${f}`);
          return secondInterval;
        })
      )
      /*
        When we subscribed to the first interval, it starts to emit a values (starting 0).
        This value is mapped to the second interval which then begins to emit (starting 0).
        While the second interval is active, values from the first interval are ignored.
        We can see this when firstInterval emits number 3,6, and so on...

          Output:
          Emission of first interval: 0
          0
          1
          Emission of first interval: 3
          0
          1
          Emission of first interval: 6
          0
          1
          Emission of first interval: 9
          0
          1
      */
      .subscribe(s => console.log(s));
  }

> => (
  action$,
  state$,
  { selectMetricTimeUpdatePolicyInterval, selectMetricRangeFromTimeRange }
) => {
  const updateInterval$ = state$.pipe(
    map(selectMetricTimeUpdatePolicyInterval),
    filter(isNotNull)
  );

  const range$ = state$.pipe(
    map(selectMetricRangeFromTimeRange),
    filter(isNotNull)
  );

  return action$.pipe(
    filter(startMetricsAutoReload.match),
    withLatestFrom(updateInterval$, range$),
    exhaustMap(([action, updateInterval, range]) =>
      timer(0, updateInterval).pipe(
        map(() =>
          setRangeTime({
            from: moment()
              .subtract(range, 'ms')
              .valueOf(),
            to: moment().valueOf(),
            interval: '1m',
          })
        ),
        takeUntil(action$.pipe(filter(stopMetricsAutoReload.match)))
      )
    )
  );
};

  it('should not break unsubscription chains when result is unsubscribed explicitly', () => {
    const x = cold(     '--a--b--c--|                               ');
    const xsubs =    '   ^          !                               ';
    const y = cold(               '--d--e--f--|                     ');
    const ysubs: string[] = [];
    const z = cold(                                 '--g--h--i--|   ');
    const zsubs =    '                               ^  !           ';
    const e1 =   hot('---x---------y-----------------z-------------|');
    const e1subs =   '^                                 !           ';
    const expected = '-----a--b--c---------------------g-           ';
    const unsub =    '                                  !           ';

    const observableLookup = { x: x, y: y, z: z };

    const result = e1.pipe(
      mergeMap(x => of(x)),
      exhaustMap(value => observableLookup[value]),
      mergeMap(x => of(x))
    );

    expectObservable(result, unsub).toBe(expected);
    expectSubscriptions(x.subscriptions).toBe(xsubs);
    expectSubscriptions(y.subscriptions).toBe(ysubs);
    expectSubscriptions(z.subscriptions).toBe(zsubs);
    expectSubscriptions(e1.subscriptions).toBe(e1subs);
  });

  exhaustMap1() {
    const sourceInterval = interval(1000);
    const delayedInterval = sourceInterval.pipe(delay(10), take(4));

    const exhaustSub = merge(
      //  delay 10ms, then start interval emitting 4 values
      delayedInterval,
      //  emit immediately
      of(true)
    )
      .pipe(exhaustMap(_ => sourceInterval.pipe(take(5))))
      /*
       *  The first emitted value (of(true)) will be mapped
       *  to an interval observable emitting 1 value every
       *  second, completing after 5.
       *  Because the emissions from the delayed interval
       *  fall while this observable is still active they will be ignored.
       *
       *  Contrast this with concatMap which would queue,
       *  switchMap which would switch to a new inner observable each emission,
       *  and mergeMap which would maintain a new subscription for each emitted value.
       */
      //  output: 0, 1, 2, 3, 4
      .subscribe(val => console.log(val));
  }

export const createLogPositionEpic = <State>(): Epic<Action, Action, State, {}> => action$ =>
  action$.pipe(
    filter(startAutoReload.match),
    exhaustMap(({ payload }) =>
      timer(0, payload).pipe(
        map(() => jumpToTargetPositionTime(Date.now())),
        takeUntil(action$.pipe(filter(stopAutoReload.match)))
      )
    )
  );

  ('should map-and-flatten each item to an Observable', () => {
    const e1 =    hot('--1-----3--5-------|');
    const e1subs =    '^                  !';
    const e2 =   cold('x-x-x|              ', {x: 10});
    const expected =  '--x-x-x-y-y-y------|';
    const values = {x: 10, y: 30, z: 50};

    const result = e1.pipe(exhaustMap(x => e2.map(i => i * +x)));

    expectObservable(result).toBe(expected, values);
    expectSubscriptions(e1.subscriptions).toBe(e1subs);
  });