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Subject.ts
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Subject.ts
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import { Operator } from './Operator';
import { Observable } from './Observable';
import { Subscriber } from './Subscriber';
import { Subscription, EMPTY_SUBSCRIPTION } from './Subscription';
import { Observer, SubscriptionLike, TeardownLogic } from './types';
import { ObjectUnsubscribedError } from './util/ObjectUnsubscribedError';
import { arrRemove } from './util/arrRemove';
import { errorContext } from './util/errorContext';
/**
* A Subject is a special type of Observable that allows values to be
* multicasted to many Observers. Subjects are like EventEmitters.
*
* Every Subject is an Observable and an Observer. You can subscribe to a
* Subject, and you can call next to feed values as well as error and complete.
*/
export class Subject<T> extends Observable<T> implements SubscriptionLike {
closed = false;
private currentObservers: Observer<T>[] | null = null;
/** @deprecated Internal implementation detail, do not use directly. Will be made internal in v8. */
observers: Observer<T>[] = [];
/** @deprecated Internal implementation detail, do not use directly. Will be made internal in v8. */
isStopped = false;
/** @deprecated Internal implementation detail, do not use directly. Will be made internal in v8. */
hasError = false;
/** @deprecated Internal implementation detail, do not use directly. Will be made internal in v8. */
thrownError: any = null;
/**
* Creates a "subject" by basically gluing an observer to an observable.
*
* @nocollapse
* @deprecated Recommended you do not use. Will be removed at some point in the future. Plans for replacement still under discussion.
*/
static create: (...args: any[]) => any = <T>(destination: Observer<T>, source: Observable<T>): AnonymousSubject<T> => {
return new AnonymousSubject<T>(destination, source);
};
constructor() {
// NOTE: This must be here to obscure Observable's constructor.
super();
}
/** @deprecated Internal implementation detail, do not use directly. Will be made internal in v8. */
lift<R>(operator: Operator<T, R>): Observable<R> {
const subject = new AnonymousSubject(this, this);
subject.operator = operator as any;
return subject as any;
}
/** @internal */
protected _throwIfClosed() {
if (this.closed) {
throw new ObjectUnsubscribedError();
}
}
next(value: T) {
errorContext(() => {
this._throwIfClosed();
if (!this.isStopped) {
if (!this.currentObservers) {
this.currentObservers = Array.from(this.observers);
}
for (const observer of this.currentObservers) {
observer.next(value);
}
}
});
}
error(err: any) {
errorContext(() => {
this._throwIfClosed();
if (!this.isStopped) {
this.hasError = this.isStopped = true;
this.thrownError = err;
const { observers } = this;
while (observers.length) {
observers.shift()!.error(err);
}
}
});
}
complete() {
errorContext(() => {
this._throwIfClosed();
if (!this.isStopped) {
this.isStopped = true;
const { observers } = this;
while (observers.length) {
observers.shift()!.complete();
}
}
});
}
unsubscribe() {
this.isStopped = this.closed = true;
this.observers = this.currentObservers = null!;
}
get observed() {
return this.observers?.length > 0;
}
/** @internal */
protected _trySubscribe(subscriber: Subscriber<T>): TeardownLogic {
this._throwIfClosed();
return super._trySubscribe(subscriber);
}
/** @internal */
protected _subscribe(subscriber: Subscriber<T>): Subscription {
this._throwIfClosed();
this._checkFinalizedStatuses(subscriber);
return this._innerSubscribe(subscriber);
}
/** @internal */
protected _innerSubscribe(subscriber: Subscriber<any>) {
const { hasError, isStopped, observers } = this;
if (hasError || isStopped) {
return EMPTY_SUBSCRIPTION;
}
this.currentObservers = null;
observers.push(subscriber);
return new Subscription(() => {
this.currentObservers = null;
arrRemove(observers, subscriber);
});
}
/** @internal */
protected _checkFinalizedStatuses(subscriber: Subscriber<any>) {
const { hasError, thrownError, isStopped } = this;
if (hasError) {
subscriber.error(thrownError);
} else if (isStopped) {
subscriber.complete();
}
}
/**
* Creates a new Observable with this Subject as the source. You can do this
* to create customize Observer-side logic of the Subject and conceal it from
* code that uses the Observable.
* @return {Observable} Observable that the Subject casts to
*/
asObservable(): Observable<T> {
const observable: any = new Observable<T>();
observable.source = this;
return observable;
}
}
/**
* @class AnonymousSubject<T>
*/
export class AnonymousSubject<T> extends Subject<T> {
constructor(
/** @deprecated Internal implementation detail, do not use directly. Will be made internal in v8. */
public destination?: Observer<T>,
source?: Observable<T>
) {
super();
this.source = source;
}
next(value: T) {
this.destination?.next?.(value);
}
error(err: any) {
this.destination?.error?.(err);
}
complete() {
this.destination?.complete?.();
}
/** @internal */
protected _subscribe(subscriber: Subscriber<T>): Subscription {
return this.source?.subscribe(subscriber) ?? EMPTY_SUBSCRIPTION;
}
}