| import { Subscriber } from '../Subscriber'; |
| import { ArgumentOutOfRangeError } from '../util/ArgumentOutOfRangeError'; |
| import { EmptyObservable } from '../observable/EmptyObservable'; |
| /** |
| * Emits only the first `count` values emitted by the source Observable. |
| * |
| * <span class="informal">Takes the first `count` values from the source, then |
| * completes.</span> |
| * |
| * <img src="./img/take.png" width="100%"> |
| * |
| * `take` returns an Observable that emits only the first `count` values emitted |
| * by the source Observable. If the source emits fewer than `count` values then |
| * all of its values are emitted. After that, it completes, regardless if the |
| * source completes. |
| * |
| * @example <caption>Take the first 5 seconds of an infinite 1-second interval Observable</caption> |
| * var interval = Rx.Observable.interval(1000); |
| * var five = interval.take(5); |
| * five.subscribe(x => console.log(x)); |
| * |
| * @see {@link takeLast} |
| * @see {@link takeUntil} |
| * @see {@link takeWhile} |
| * @see {@link skip} |
| * |
| * @throws {ArgumentOutOfRangeError} When using `take(i)`, it delivers an |
| * ArgumentOutOrRangeError to the Observer's `error` callback if `i < 0`. |
| * |
| * @param {number} count The maximum number of `next` values to emit. |
| * @return {Observable<T>} An Observable that emits only the first `count` |
| * values emitted by the source Observable, or all of the values from the source |
| * if the source emits fewer than `count` values. |
| * @method take |
| * @owner Observable |
| */ |
| export function take(count) { |
| return (source) => { |
| if (count === 0) { |
| return new EmptyObservable(); |
| } |
| else { |
| return source.lift(new TakeOperator(count)); |
| } |
| }; |
| } |
| class TakeOperator { |
| constructor(total) { |
| this.total = total; |
| if (this.total < 0) { |
| throw new ArgumentOutOfRangeError; |
| } |
| } |
| call(subscriber, source) { |
| return source.subscribe(new TakeSubscriber(subscriber, this.total)); |
| } |
| } |
| /** |
| * We need this JSDoc comment for affecting ESDoc. |
| * @ignore |
| * @extends {Ignored} |
| */ |
| class TakeSubscriber extends Subscriber { |
| constructor(destination, total) { |
| super(destination); |
| this.total = total; |
| this.count = 0; |
| } |
| _next(value) { |
| const total = this.total; |
| const count = ++this.count; |
| if (count <= total) { |
| this.destination.next(value); |
| if (count === total) { |
| this.destination.complete(); |
| this.unsubscribe(); |
| } |
| } |
| } |
| } |
| //# sourceMappingURL=take.js.map |