@reactivex/rxjs
Version:
Reactive Extensions for modern JavaScript
160 lines • 6.2 kB
JavaScript
;
var __extends = (this && this.__extends) || (function () {
var extendStatics = function (d, b) {
extendStatics = Object.setPrototypeOf ||
({ __proto__: [] } instanceof Array && function (d, b) { d.__proto__ = b; }) ||
function (d, b) { for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p]; };
return extendStatics(d, b);
}
return function (d, b) {
extendStatics(d, b);
function __() { this.constructor = d; }
d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
};
})();
Object.defineProperty(exports, "__esModule", { value: true });
var map_1 = require("./map");
var from_1 = require("../observable/from");
var innerSubscribe_1 = require("../innerSubscribe");
/* tslint:enable:max-line-length */
/**
* Projects each source value to an Observable which is merged in the output
* Observable, emitting values only from the most recently projected Observable.
*
* <span class="informal">Maps each value to an Observable, then flattens all of
* these inner Observables.</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 time it observes one of these
* inner Observables, the output Observable begins emitting the items emitted by
* that inner Observable. When a new inner Observable is emitted, `switchMap`
* stops emitting items from the earlier-emitted inner Observable and begins
* emitting items from the new one. It continues to behave like this for
* subsequent inner Observables.
*
* ## Example
* Generate new Observable according to source Observable values
* ```typescript
* import { of } from 'rxjs';
* import { switchMap } from 'rxjs/operators';
*
* const switched = of(1, 2, 3).pipe(switchMap((x: number) => of(x, x ** 2, x ** 3)));
* switched.subscribe(x => console.log(x));
* // outputs
* // 1
* // 1
* // 1
* // 2
* // 4
* // 8
* // ... and so on
* ```
*
* Rerun an interval Observable on every click event
* ```ts
* import { fromEvent, interval } from 'rxjs';
* import { switchMap } from 'rxjs/operators';
*
* const clicks = fromEvent(document, 'click');
* const result = clicks.pipe(switchMap((ev) => interval(1000)));
* result.subscribe(x => console.log(x));
* ```
*
* @see {@link concatMap}
* @see {@link exhaustMap}
* @see {@link mergeMap}
* @see {@link switchAll}
* @see {@link switchMapTo}
*
* @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 only the values from the most recently
* projected inner Observable.
* @method switchMap
* @owner Observable
*/
function switchMap(project, resultSelector) {
if (typeof resultSelector === 'function') {
return function (source) { return source.pipe(switchMap(function (a, i) { return from_1.from(project(a, i)).pipe(map_1.map(function (b, ii) { return resultSelector(a, b, i, ii); })); })); };
}
return function (source) { return source.lift(new SwitchMapOperator(project)); };
}
exports.switchMap = switchMap;
var SwitchMapOperator = /** @class */ (function () {
function SwitchMapOperator(project) {
this.project = project;
}
SwitchMapOperator.prototype.call = function (subscriber, source) {
return source.subscribe(new SwitchMapSubscriber(subscriber, this.project));
};
return SwitchMapOperator;
}());
/**
* We need this JSDoc comment for affecting ESDoc.
* @ignore
* @extends {Ignored}
*/
var SwitchMapSubscriber = /** @class */ (function (_super) {
__extends(SwitchMapSubscriber, _super);
function SwitchMapSubscriber(destination, project) {
var _this = _super.call(this, destination) || this;
_this.project = project;
_this.index = 0;
return _this;
}
SwitchMapSubscriber.prototype._next = function (value) {
var result;
var index = this.index++;
try {
result = this.project(value, index);
}
catch (error) {
this.destination.error(error);
return;
}
this._innerSub(result);
};
SwitchMapSubscriber.prototype._innerSub = function (result) {
var innerSubscription = this.innerSubscription;
if (innerSubscription) {
innerSubscription.unsubscribe();
}
var innerSubscriber = new innerSubscribe_1.SimpleInnerSubscriber(this);
var destination = this.destination;
destination.add(innerSubscriber);
this.innerSubscription = innerSubscribe_1.innerSubscribe(result, innerSubscriber);
// The returned subscription will usually be the subscriber that was
// passed. However, interop subscribers will be wrapped and for
// unsubscriptions to chain correctly, the wrapper needs to be added, too.
if (this.innerSubscription !== innerSubscriber) {
destination.add(this.innerSubscription);
}
};
SwitchMapSubscriber.prototype._complete = function () {
var innerSubscription = this.innerSubscription;
if (!innerSubscription || innerSubscription.closed) {
_super.prototype._complete.call(this);
}
this.unsubscribe();
};
SwitchMapSubscriber.prototype._unsubscribe = function () {
this.innerSubscription = undefined;
};
SwitchMapSubscriber.prototype.notifyComplete = function () {
this.innerSubscription = undefined;
if (this.isStopped) {
_super.prototype._complete.call(this);
}
};
SwitchMapSubscriber.prototype.notifyNext = function (innerValue) {
this.destination.next(innerValue);
};
return SwitchMapSubscriber;
}(innerSubscribe_1.SimpleOuterSubscriber));
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