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1 | import {Observable} from '../Observable';
import {Operator} from '../Operator';
import {Subscriber} from '../Subscriber';
import {Subscription} from '../Subscription';
import {tryCatch} from '../util/tryCatch';
import {errorObject} from '../util/errorObject';
import {subscribeToResult} from '../util/subscribeToResult';
import {OuterSubscriber} from '../OuterSubscriber';
/**
* Returns an Observable that emits items based on applying a function that you supply to each item emitted by the
* source Observable, where that function returns an Observable, and then merging those resulting Observables and
* emitting the results of this merger.
*
* <img src="./img/mergeMap.png" width="100%">
*
* @param {Function} a function that, when applied to an item emitted by the source Observable, returns an Observable.
* @returns {Observable} an Observable that emits the result of applying the transformation function to each item
* emitted by the source Observable and merging the results of the Observables obtained from this transformation
*/
export function mergeMap<T, R, R2>(project: (value: T, index: number) => Observable<R>,
resultSelector?: (outerValue: T, innerValue: R, outerIndex: number, innerIndex: number) => R2 | number,
concurrent: number = Number.POSITIVE_INFINITY): Observable<R2> {
return this.lift(new MergeMapOperator(project, <any>resultSelector, concurrent));
}
export class MergeMapOperator<T, R, R2> implements Operator<T, R> {
constructor(private project: (value: T, index: number) => Observable<R>,
private resultSelector?: (outerValue: T, innerValue: R, outerIndex: number, innerIndex: number) => R2,
Iprivate concurrent: number = Number.POSITIVE_INFINITY) {
}
call(observer: Subscriber<R>): Subscriber<T> {
return new MergeMapSubscriber(
observer, this.project, this.resultSelector, this.concurrent
);
}
}
export class MergeMapSubscriber<T, R, R2> extends OuterSubscriber<T, R> {
private hasCompleted: boolean = false;
private buffer: Observable<any>[] = [];
private active: number = 0;
protected index: number = 0;
constructor(destination: Subscriber<R>,
private project: (value: T, index: number) => Observable<R>,
private resultSelector?: (outerValue: T, innerValue: R, outerIndex: number, innerIndex: number) => R2,
Iprivate concurrent: number = Number.POSITIVE_INFINITY) {
super(destination);
}
protected _next(value: any): void {
if (this.active < this.concurrent) {
const index = this.index++;
const ish = tryCatch(this.project)(value, index);
const destination = this.destination;
if (ish === errorObject) {
destination.error(errorObject.e);
} else {
this.active++;
this._innerSub(ish, value, index);
}
} else {
this.buffer.push(value);
}
}
private _innerSub(ish: any, value: T, index: number): void {
this.add(subscribeToResult<T, R>(this, ish, value, index));
}
protected _complete(): void {
this.hasCompleted = true;
if (this.active === 0 && this.buffer.length === 0) {
this.destination.complete();
}
}
notifyNext(outerValue: T, innerValue: R, outerIndex: number, innerIndex: number): void {
const { destination, resultSelector } = this;
if (resultSelector) {
const result = tryCatch(resultSelector)(outerValue, innerValue, outerIndex, innerIndex);
if (result === errorObject) {
destination.error(errorObject.e);
} else {
destination.next(result);
}
} else {
destination.next(innerValue);
}
}
notifyComplete(innerSub: Subscription): void {
const buffer = this.buffer;
this.remove(innerSub);
this.active--;
if (buffer.length > 0) {
this._next(buffer.shift());
} else if (this.active === 0 && this.hasCompleted) {
this.destination.complete();
}
}
} |