| import {Observable} from '../Observable'; |
| import {Operator} from '../Operator'; |
| import {Subscriber} from '../Subscriber'; |
| import {OperatorFunction} from '../types'; |
| |
| export function find<T, S extends T>(predicate: (value: T, index: number, source: Observable<T>) => value is S, |
| thisArg?: any): OperatorFunction<T, S | undefined>; |
| export function find<T>(predicate: (value: T, index: number, source: Observable<T>) => boolean, |
| thisArg?: any): OperatorFunction<T, T | undefined>; |
| /** |
| * 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> |
| * |
| * ![](find.png) |
| * |
| * `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 |
| * Find and emit the first click that happens on a DIV element |
| * ```ts |
| * import { fromEvent } from 'rxjs'; |
| * import { find } from 'rxjs/operators'; |
| * |
| * const clicks = fromEvent(document, 'click'); |
| * const result = clicks.pipe(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<T>(predicate: (value: T, index: number, source: Observable<T>) => boolean, |
| thisArg?: any): OperatorFunction<T, T | undefined> { |
| if (typeof predicate !== 'function') { |
| throw new TypeError('predicate is not a function'); |
| } |
| return (source: Observable<T>) => source.lift(new FindValueOperator(predicate, source, false, thisArg)) as Observable<T | undefined>; |
| } |
| |
| export class FindValueOperator<T> implements Operator<T, T | number | undefined> { |
| constructor(private predicate: (value: T, index: number, source: Observable<T>) => boolean, |
| private source: Observable<T>, |
| private yieldIndex: boolean, |
| private thisArg?: any) { |
| } |
| |
| call(observer: Subscriber<T>, source: any): any { |
| 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<T> extends Subscriber<T> { |
| private index: number = 0; |
| |
| constructor(destination: Subscriber<T>, |
| private predicate: (value: T, index: number, source: Observable<T>) => boolean, |
| private source: Observable<T>, |
| private yieldIndex: boolean, |
| private thisArg?: any) { |
| super(destination); |
| } |
| |
| private notifyComplete(value: any): void { |
| const destination = this.destination; |
| |
| destination.next(value); |
| destination.complete(); |
| this.unsubscribe(); |
| } |
| |
| protected _next(value: T): void { |
| 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); |
| } |
| } |
| |
| protected _complete(): void { |
| this.notifyComplete(this.yieldIndex ? -1 : undefined); |
| } |
| } |