@reactivex/rxjs
Version:
Reactive Extensions for modern JavaScript
169 lines • 7.2 kB
JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
var Observable_1 = require("../Observable");
var isArray_1 = require("../util/isArray");
var map_1 = require("../operators/map");
var isObject_1 = require("../util/isObject");
var from_1 = require("./from");
/* tslint:enable:max-line-length */
/**
* Accepts an `Array` of {@link ObservableInput} or a dictionary `Object` of {@link ObservableInput} and returns
* an {@link Observable} that emits either an array of values in the exact same order as the passed array,
* or a dictionary of values in the same shape as the passed dictionary.
*
* <span class="informal">Wait for Observables to complete and then combine last values they emitted.</span>
*
* 
*
* `forkJoin` is an operator that takes any number of input observables which can be passed either as an array
* or a dictionary of input observables. If no input observables are provided, resulting stream will complete
* immediately.
*
* `forkJoin` will wait for all passed observables to complete and then it will emit an array or an object with last
* values from corresponding observables.
*
* If you pass an array of `n` observables to the operator, resulting
* array will have `n` values, where first value is the last thing emitted by the first observable,
* second value is the last thing emitted by the second observable and so on.
*
* If you pass a dictionary of observables to the operator, resulting
* objects will have the same keys as the dictionary passed, with their last values they've emitted
* located at the corresponding key.
*
* That means `forkJoin` will not emit more than once and it will complete after that. If you need to emit combined
* values not only at the end of lifecycle of passed observables, but also throughout it, try out {@link combineLatest}
* or {@link zip} instead.
*
* In order for resulting array to have the same length as the number of input observables, whenever any of
* that observables completes without emitting any value, `forkJoin` will complete at that moment as well
* and it will not emit anything either, even if it already has some last values from other observables.
* Conversely, if there is an observable that never completes, `forkJoin` will never complete as well,
* unless at any point some other observable completes without emitting value, which brings us back to
* the previous case. Overall, in order for `forkJoin` to emit a value, all observables passed as arguments
* have to emit something at least once and complete.
*
* If any input observable errors at some point, `forkJoin` will error as well and all other observables
* will be immediately unsubscribed.
*
* Optionally `forkJoin` accepts project function, that will be called with values which normally
* would land in emitted array. Whatever is returned by project function, will appear in output
* observable instead. This means that default project can be thought of as a function that takes
* all its arguments and puts them into an array. Note that project function will be called only
* when output observable is supposed to emit a result.
*
* ## Examples
*
* ### Use forkJoin with a dictionary of observable inputs
* ```ts
* import { forkJoin, of, timer } from 'rxjs';
*
* const observable = forkJoin({
* foo: of(1, 2, 3, 4),
* bar: Promise.resolve(8),
* baz: timer(4000),
* });
* observable.subscribe({
* next: value => console.log(value),
* complete: () => console.log('This is how it ends!'),
* });
*
* // Logs:
* // { foo: 4, bar: 8, baz: 0 } after 4 seconds
* // "This is how it ends!" immediately after
* ```
*
* ### Use forkJoin with an array of observable inputs
* ```ts
* import { forkJoin, of } from 'rxjs';
*
* const observable = forkJoin([
* of(1, 2, 3, 4),
* Promise.resolve(8),
* timer(4000),
* ]);
* observable.subscribe({
* next: value => console.log(value),
* complete: () => console.log('This is how it ends!'),
* });
*
* // Logs:
* // [4, 8, 0] after 4 seconds
* // "This is how it ends!" immediately after
* ```
*
* @see {@link combineLatest}
* @see {@link zip}
*
* @param {...ObservableInput} sources Any number of Observables provided either as an array or as an arguments
* passed directly to the operator.
* @param {function} [project] Function that takes values emitted by input Observables and returns value
* that will appear in resulting Observable instead of default array.
* @return {Observable} Observable emitting either an array of last values emitted by passed Observables
* or value from project function.
*/
function forkJoin() {
var sources = [];
for (var _i = 0; _i < arguments.length; _i++) {
sources[_i] = arguments[_i];
}
if (sources.length === 1) {
var first_1 = sources[0];
if (isArray_1.isArray(first_1)) {
return forkJoinInternal(first_1, null);
}
// TODO(benlesh): isObservable check will not be necessary when deprecated path is removed.
if (isObject_1.isObject(first_1) && Object.getPrototypeOf(first_1) === Object.prototype) {
var keys = Object.keys(first_1);
return forkJoinInternal(keys.map(function (key) { return first_1[key]; }), keys);
}
}
// DEPRECATED PATHS BELOW HERE
if (typeof sources[sources.length - 1] === 'function') {
var resultSelector_1 = sources.pop();
sources = (sources.length === 1 && isArray_1.isArray(sources[0])) ? sources[0] : sources;
return forkJoinInternal(sources, null).pipe(map_1.map(function (args) { return resultSelector_1.apply(void 0, args); }));
}
return forkJoinInternal(sources, null);
}
exports.forkJoin = forkJoin;
function forkJoinInternal(sources, keys) {
return new Observable_1.Observable(function (subscriber) {
var len = sources.length;
if (len === 0) {
subscriber.complete();
return;
}
var values = new Array(len);
var completed = 0;
var emitted = 0;
var _loop_1 = function (i) {
var source = from_1.from(sources[i]);
var hasValue = false;
subscriber.add(source.subscribe({
next: function (value) {
if (!hasValue) {
hasValue = true;
emitted++;
}
values[i] = value;
},
error: function (err) { return subscriber.error(err); },
complete: function () {
completed++;
if (completed === len || !hasValue) {
if (emitted === len) {
subscriber.next(keys ?
keys.reduce(function (result, key, i) { return (result[key] = values[i], result); }, {}) :
values);
}
subscriber.complete();
}
}
}));
};
for (var i = 0; i < len; i++) {
_loop_1(i);
}
});
}
//# sourceMappingURL=forkJoin.js.map