Current File : //home/forge/takeaseat.eco-n-tech.co.uk/node_modules/rxjs/src/internal/operators/find.ts
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` 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);
}
}
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