| import { Subscriber } from '../Subscriber'; |
| /** |
| * Emits only the first value emitted by the source Observable that meets some |
| * condition. |
| * |
| * <span class="informal">Finds the first value that passes some test and emits |
| * that.</span> |
| * |
| * <img src="./img/find.png" width="100%"> |
| * |
| * `find` searches for the first item in the source Observable that matches the |
| * specified condition embodied by the `predicate`, and returns the first |
| * occurrence in the source. Unlike {@link first}, the `predicate` is required |
| * in `find`, and does not emit an error if a valid value is not found. |
| * |
| * @example <caption>Find and emit the first click that happens on a DIV element</caption> |
| * var clicks = Rx.Observable.fromEvent(document, 'click'); |
| * var result = clicks.find(ev => ev.target.tagName === 'DIV'); |
| * result.subscribe(x => console.log(x)); |
| * |
| * @see {@link filter} |
| * @see {@link first} |
| * @see {@link findIndex} |
| * @see {@link take} |
| * |
| * @param {function(value: T, index: number, source: Observable<T>): boolean} predicate |
| * A function called with each item to test for condition matching. |
| * @param {any} [thisArg] An optional argument to determine the value of `this` |
| * in the `predicate` function. |
| * @return {Observable<T>} An Observable of the first item that matches the |
| * condition. |
| * @method find |
| * @owner Observable |
| */ |
| export function find(predicate, thisArg) { |
| if (typeof predicate !== 'function') { |
| throw new TypeError('predicate is not a function'); |
| } |
| return (source) => source.lift(new FindValueOperator(predicate, source, false, thisArg)); |
| } |
| export class FindValueOperator { |
| constructor(predicate, source, yieldIndex, thisArg) { |
| this.predicate = predicate; |
| this.source = source; |
| this.yieldIndex = yieldIndex; |
| this.thisArg = thisArg; |
| } |
| call(observer, source) { |
| return source.subscribe(new FindValueSubscriber(observer, this.predicate, this.source, this.yieldIndex, this.thisArg)); |
| } |
| } |
| /** |
| * We need this JSDoc comment for affecting ESDoc. |
| * @ignore |
| * @extends {Ignored} |
| */ |
| export class FindValueSubscriber extends Subscriber { |
| constructor(destination, predicate, source, yieldIndex, thisArg) { |
| super(destination); |
| this.predicate = predicate; |
| this.source = source; |
| this.yieldIndex = yieldIndex; |
| this.thisArg = thisArg; |
| this.index = 0; |
| } |
| notifyComplete(value) { |
| const destination = this.destination; |
| destination.next(value); |
| destination.complete(); |
| } |
| _next(value) { |
| const { predicate, thisArg } = this; |
| const index = this.index++; |
| try { |
| const result = predicate.call(thisArg || this, value, index, this.source); |
| if (result) { |
| this.notifyComplete(this.yieldIndex ? index : value); |
| } |
| } |
| catch (err) { |
| this.destination.error(err); |
| } |
| } |
| _complete() { |
| this.notifyComplete(this.yieldIndex ? -1 : undefined); |
| } |
| } |
| //# sourceMappingURL=find.js.map |