import {Observable} from '../Observable';
import {Operator} from '../Operator';
import {Subscriber} from '../Subscriber';
import {tryCatch} from '../util/tryCatch';
import {errorObject} from '../util/errorObject';
/**
* Returns an Observable that searches for the first item in the source Observable that
* matches the specified condition, and returns the first occurence in the source.
* @param {function} predicate function called with each item to test for condition matching.
* @returns {Observable} an Observable of the first item that matches the condition.
*/
export function find<T>(predicate: (value: T, index: number, source: Observable<T>) => boolean, thisArg?: any): Observable<T> {
if (typeof predicate !== 'function') {
throw new TypeError('predicate is not a function');
}
return this.lift(new FindValueOperator(predicate, this, false, thisArg));
}
export class FindValueOperator<T> implements Operator<T, T> {
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>): Subscriber<T> {
return new FindValueSubscriber(observer, this.predicate, this.source, this.yieldIndex, this.thisArg);
}
}
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();
}
protected _next(value: T): void {
const { predicate, thisArg } = this;
const index = this.index++;
const result = tryCatch(predicate).call(thisArg || this, value, index, this.source);
if (result === errorObject) {
this.destination.error(result.e);
} else if (result) {
this.notifyComplete(this.yieldIndex ? index : value);
}
}
protected _complete(): void {
this.notifyComplete(this.yieldIndex ? -1 : undefined);
}
} |