@reactivex/rxjs
Version:
Reactive Extensions for modern JavaScript
133 lines • 4.7 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 Subscriber_1 = require("../Subscriber");
var EmptyError_1 = require("../util/EmptyError");
/**
* Returns an Observable that emits the single item emitted by the source Observable that matches a specified
* predicate, if that Observable emits one such item. If the source Observable emits more than one such item or no
* items, notify of an IllegalArgumentException or NoSuchElementException respectively. If the source Observable
* emits items but none match the specified predicate then `undefined` is emitted.
*
* <span class="informal">Like {@link first}, but emit with error notification if there is more than one value.</span>
* 
*
* ## Example
* emits 'error'
* ```ts
* import { range } from 'rxjs';
* import { single } from 'rxjs/operators';
*
* const numbers = range(1,5).pipe(single());
* numbers.subscribe(x => console.log('never get called'), e => console.log('error'));
* // result
* // 'error'
* ```
*
* emits 'undefined'
* ```ts
* import { range } from 'rxjs';
* import { single } from 'rxjs/operators';
*
* const numbers = range(1,5).pipe(single(x => x === 10));
* numbers.subscribe(x => console.log(x));
* // result
* // 'undefined'
* ```
*
* @see {@link first}
* @see {@link find}
* @see {@link findIndex}
* @see {@link elementAt}
*
* @throws {EmptyError} Delivers an EmptyError to the Observer's `error`
* callback if the Observable completes before any `next` notification was sent.
* @param {Function} predicate - A predicate function to evaluate items emitted by the source Observable.
* @return {Observable<T>} An Observable that emits the single item emitted by the source Observable that matches
* the predicate or `undefined` when no items match.
*
* @method single
* @owner Observable
*/
function single(predicate) {
return function (source) { return source.lift(new SingleOperator(predicate, source)); };
}
exports.single = single;
var SingleOperator = /** @class */ (function () {
function SingleOperator(predicate, source) {
this.predicate = predicate;
this.source = source;
}
SingleOperator.prototype.call = function (subscriber, source) {
return source.subscribe(new SingleSubscriber(subscriber, this.predicate, this.source));
};
return SingleOperator;
}());
/**
* We need this JSDoc comment for affecting ESDoc.
* @ignore
* @extends {Ignored}
*/
var SingleSubscriber = /** @class */ (function (_super) {
__extends(SingleSubscriber, _super);
function SingleSubscriber(destination, predicate, source) {
var _this = _super.call(this, destination) || this;
_this.predicate = predicate;
_this.source = source;
_this.seenValue = false;
_this.index = 0;
return _this;
}
SingleSubscriber.prototype.applySingleValue = function (value) {
if (this.seenValue) {
this.destination.error('Sequence contains more than one element');
}
else {
this.seenValue = true;
this.singleValue = value;
}
};
SingleSubscriber.prototype._next = function (value) {
var index = this.index++;
if (this.predicate) {
this.tryNext(value, index);
}
else {
this.applySingleValue(value);
}
};
SingleSubscriber.prototype.tryNext = function (value, index) {
try {
if (this.predicate(value, index, this.source)) {
this.applySingleValue(value);
}
}
catch (err) {
this.destination.error(err);
}
};
SingleSubscriber.prototype._complete = function () {
var destination = this.destination;
if (this.index > 0) {
destination.next(this.seenValue ? this.singleValue : undefined);
destination.complete();
}
else {
destination.error(new EmptyError_1.EmptyError);
}
};
return SingleSubscriber;
}(Subscriber_1.Subscriber));
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