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- import { Observable } from '../Observable';
- import { ObservableInput, SchedulerLike, ObservedValueOf, ObservableInputTuple } from '../types';
- import { argsArgArrayOrObject } from '../util/argsArgArrayOrObject';
- import { Subscriber } from '../Subscriber';
- import { from } from './from';
- import { identity } from '../util/identity';
- import { Subscription } from '../Subscription';
- import { mapOneOrManyArgs } from '../util/mapOneOrManyArgs';
- import { popResultSelector, popScheduler } from '../util/args';
- import { createObject } from '../util/createObject';
- import { createOperatorSubscriber } from '../operators/OperatorSubscriber';
- import { AnyCatcher } from '../AnyCatcher';
- import { executeSchedule } from '../util/executeSchedule';
- // combineLatest(any)
- // We put this first because we need to catch cases where the user has supplied
- // _exactly `any`_ as the argument. Since `any` literally matches _anything_,
- // we don't want it to randomly hit one of the other type signatures below,
- // as we have no idea at build-time what type we should be returning when given an any.
- /**
- * You have passed `any` here, we can't figure out if it is
- * an array or an object, so you're getting `unknown`. Use better types.
- * @param arg Something typed as `any`
- */
- export function combineLatest<T extends AnyCatcher>(arg: T): Observable<unknown>;
- // combineLatest([a, b, c])
- export function combineLatest(sources: []): Observable<never>;
- export function combineLatest<A extends readonly unknown[]>(sources: readonly [...ObservableInputTuple<A>]): Observable<A>;
- /** @deprecated The `scheduler` parameter will be removed in v8. Use `scheduled` and `combineLatestAll`. Details: https://rxjs.dev/deprecations/scheduler-argument */
- export function combineLatest<A extends readonly unknown[], R>(
- sources: readonly [...ObservableInputTuple<A>],
- resultSelector: (...values: A) => R,
- scheduler: SchedulerLike
- ): Observable<R>;
- export function combineLatest<A extends readonly unknown[], R>(
- sources: readonly [...ObservableInputTuple<A>],
- resultSelector: (...values: A) => R
- ): Observable<R>;
- /** @deprecated The `scheduler` parameter will be removed in v8. Use `scheduled` and `combineLatestAll`. Details: https://rxjs.dev/deprecations/scheduler-argument */
- export function combineLatest<A extends readonly unknown[]>(
- sources: readonly [...ObservableInputTuple<A>],
- scheduler: SchedulerLike
- ): Observable<A>;
- // combineLatest(a, b, c)
- /** @deprecated Pass an array of sources instead. The rest-parameters signature will be removed in v8. Details: https://rxjs.dev/deprecations/array-argument */
- export function combineLatest<A extends readonly unknown[]>(...sources: [...ObservableInputTuple<A>]): Observable<A>;
- /** @deprecated The `scheduler` parameter will be removed in v8. Use `scheduled` and `combineLatestAll`. Details: https://rxjs.dev/deprecations/scheduler-argument */
- export function combineLatest<A extends readonly unknown[], R>(
- ...sourcesAndResultSelectorAndScheduler: [...ObservableInputTuple<A>, (...values: A) => R, SchedulerLike]
- ): Observable<R>;
- /** @deprecated Pass an array of sources instead. The rest-parameters signature will be removed in v8. Details: https://rxjs.dev/deprecations/array-argument */
- export function combineLatest<A extends readonly unknown[], R>(
- ...sourcesAndResultSelector: [...ObservableInputTuple<A>, (...values: A) => R]
- ): Observable<R>;
- /** @deprecated The `scheduler` parameter will be removed in v8. Use `scheduled` and `combineLatestAll`. Details: https://rxjs.dev/deprecations/scheduler-argument */
- export function combineLatest<A extends readonly unknown[]>(
- ...sourcesAndScheduler: [...ObservableInputTuple<A>, SchedulerLike]
- ): Observable<A>;
- // combineLatest({a, b, c})
- export function combineLatest(sourcesObject: { [K in any]: never }): Observable<never>;
- export function combineLatest<T extends Record<string, ObservableInput<any>>>(
- sourcesObject: T
- ): Observable<{ [K in keyof T]: ObservedValueOf<T[K]> }>;
- /**
- * Combines multiple Observables to create an Observable whose values are
- * calculated from the latest values of each of its input Observables.
- *
- * <span class="informal">Whenever any input Observable emits a value, it
- * computes a formula using the latest values from all the inputs, then emits
- * the output of that formula.</span>
- *
- * 
- *
- * `combineLatest` combines the values from all the Observables passed in the
- * observables array. This is done by subscribing to each Observable in order and,
- * whenever any Observable emits, collecting an array of the most recent
- * values from each Observable. So if you pass `n` Observables to this operator,
- * the returned Observable will always emit an array of `n` values, in an order
- * corresponding to the order of the passed Observables (the value from the first Observable
- * will be at index 0 of the array and so on).
- *
- * Static version of `combineLatest` accepts an array of Observables. Note that an array of
- * Observables is a good choice, if you don't know beforehand how many Observables
- * you will combine. Passing an empty array will result in an Observable that
- * completes immediately.
- *
- * To ensure the output array always has the same length, `combineLatest` will
- * actually wait for all input Observables to emit at least once,
- * before it starts emitting results. This means if some Observable emits
- * values before other Observables started emitting, all these values but the last
- * will be lost. On the other hand, if some Observable does not emit a value but
- * completes, resulting Observable will complete at the same moment without
- * emitting anything, since it will now be impossible to include a value from the
- * completed Observable in the resulting array. Also, if some input Observable does
- * not emit any value and never completes, `combineLatest` will also never emit
- * and never complete, since, again, it will wait for all streams to emit some
- * value.
- *
- * If at least one Observable was passed to `combineLatest` and all passed Observables
- * emitted something, the resulting Observable will complete when all combined
- * streams complete. So even if some Observable completes, the result of
- * `combineLatest` will still emit values when other Observables do. In case
- * of a completed Observable, its value from now on will always be the last
- * emitted value. On the other hand, if any Observable errors, `combineLatest`
- * will error immediately as well, and all other Observables will be unsubscribed.
- *
- * ## Examples
- *
- * Combine two timer Observables
- *
- * ```ts
- * import { timer, combineLatest } from 'rxjs';
- *
- * const firstTimer = timer(0, 1000); // emit 0, 1, 2... after every second, starting from now
- * const secondTimer = timer(500, 1000); // emit 0, 1, 2... after every second, starting 0,5s from now
- * const combinedTimers = combineLatest([firstTimer, secondTimer]);
- * combinedTimers.subscribe(value => console.log(value));
- * // Logs
- * // [0, 0] after 0.5s
- * // [1, 0] after 1s
- * // [1, 1] after 1.5s
- * // [2, 1] after 2s
- * ```
- *
- * Combine a dictionary of Observables
- *
- * ```ts
- * import { of, delay, startWith, combineLatest } from 'rxjs';
- *
- * const observables = {
- * a: of(1).pipe(delay(1000), startWith(0)),
- * b: of(5).pipe(delay(5000), startWith(0)),
- * c: of(10).pipe(delay(10000), startWith(0))
- * };
- * const combined = combineLatest(observables);
- * combined.subscribe(value => console.log(value));
- * // Logs
- * // { a: 0, b: 0, c: 0 } immediately
- * // { a: 1, b: 0, c: 0 } after 1s
- * // { a: 1, b: 5, c: 0 } after 5s
- * // { a: 1, b: 5, c: 10 } after 10s
- * ```
- *
- * Combine an array of Observables
- *
- * ```ts
- * import { of, delay, startWith, combineLatest } from 'rxjs';
- *
- * const observables = [1, 5, 10].map(
- * n => of(n).pipe(
- * delay(n * 1000), // emit 0 and then emit n after n seconds
- * startWith(0)
- * )
- * );
- * const combined = combineLatest(observables);
- * combined.subscribe(value => console.log(value));
- * // Logs
- * // [0, 0, 0] immediately
- * // [1, 0, 0] after 1s
- * // [1, 5, 0] after 5s
- * // [1, 5, 10] after 10s
- * ```
- *
- * Use map operator to dynamically calculate the Body-Mass Index
- *
- * ```ts
- * import { of, combineLatest, map } from 'rxjs';
- *
- * const weight = of(70, 72, 76, 79, 75);
- * const height = of(1.76, 1.77, 1.78);
- * const bmi = combineLatest([weight, height]).pipe(
- * map(([w, h]) => w / (h * h)),
- * );
- * bmi.subscribe(x => console.log('BMI is ' + x));
- *
- * // With output to console:
- * // BMI is 24.212293388429753
- * // BMI is 23.93948099205209
- * // BMI is 23.671253629592222
- * ```
- *
- * @see {@link combineLatestAll}
- * @see {@link merge}
- * @see {@link withLatestFrom}
- *
- * @param args Any number of `ObservableInput`s provided either as an array or as an object
- * to combine with each other. If the last parameter is the function, it will be used to project the
- * values from the combined latest values into a new value on the output Observable.
- * @return An Observable of projected values from the most recent values from each `ObservableInput`,
- * or an array of the most recent values from each `ObservableInput`.
- */
- export function combineLatest<O extends ObservableInput<any>, R>(...args: any[]): Observable<R> | Observable<ObservedValueOf<O>[]> {
- const scheduler = popScheduler(args);
- const resultSelector = popResultSelector(args);
- const { args: observables, keys } = argsArgArrayOrObject(args);
- if (observables.length === 0) {
- // If no observables are passed, or someone has passed an empty array
- // of observables, or even an empty object POJO, we need to just
- // complete (EMPTY), but we have to honor the scheduler provided if any.
- return from([], scheduler as any);
- }
- const result = new Observable<ObservedValueOf<O>[]>(
- combineLatestInit(
- observables as ObservableInput<ObservedValueOf<O>>[],
- scheduler,
- keys
- ? // A handler for scrubbing the array of args into a dictionary.
- (values) => createObject(keys, values)
- : // A passthrough to just return the array
- identity
- )
- );
- return resultSelector ? (result.pipe(mapOneOrManyArgs(resultSelector)) as Observable<R>) : result;
- }
- export function combineLatestInit(
- observables: ObservableInput<any>[],
- scheduler?: SchedulerLike,
- valueTransform: (values: any[]) => any = identity
- ) {
- return (subscriber: Subscriber<any>) => {
- // The outer subscription. We're capturing this in a function
- // because we may have to schedule it.
- maybeSchedule(
- scheduler,
- () => {
- const { length } = observables;
- // A store for the values each observable has emitted so far. We match observable to value on index.
- const values = new Array(length);
- // The number of currently active subscriptions, as they complete, we decrement this number to see if
- // we are all done combining values, so we can complete the result.
- let active = length;
- // The number of inner sources that still haven't emitted the first value
- // We need to track this because all sources need to emit one value in order
- // to start emitting values.
- let remainingFirstValues = length;
- // The loop to kick off subscription. We're keying everything on index `i` to relate the observables passed
- // in to the slot in the output array or the key in the array of keys in the output dictionary.
- for (let i = 0; i < length; i++) {
- maybeSchedule(
- scheduler,
- () => {
- const source = from(observables[i], scheduler as any);
- let hasFirstValue = false;
- source.subscribe(
- createOperatorSubscriber(
- subscriber,
- (value) => {
- // When we get a value, record it in our set of values.
- values[i] = value;
- if (!hasFirstValue) {
- // If this is our first value, record that.
- hasFirstValue = true;
- remainingFirstValues--;
- }
- if (!remainingFirstValues) {
- // We're not waiting for any more
- // first values, so we can emit!
- subscriber.next(valueTransform(values.slice()));
- }
- },
- () => {
- if (!--active) {
- // We only complete the result if we have no more active
- // inner observables.
- subscriber.complete();
- }
- }
- )
- );
- },
- subscriber
- );
- }
- },
- subscriber
- );
- };
- }
- /**
- * A small utility to handle the couple of locations where we want to schedule if a scheduler was provided,
- * but we don't if there was no scheduler.
- */
- function maybeSchedule(scheduler: SchedulerLike | undefined, execute: () => void, subscription: Subscription) {
- if (scheduler) {
- executeSchedule(subscription, scheduler, execute);
- } else {
- execute();
- }
- }
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