es6/operators/refCount.js

import { Subscriber } from '../Subscriber';
export function refCount() {
    return function refCountOperatorFunction(source) {
        return source.lift(new RefCountOperator(source));
    };
}
class RefCountOperator {
    constructor(connectable) {
        this.connectable = connectable;
    }
    call(subscriber, source) {
        const { connectable } = this;
        connectable._refCount++;
        const refCounter = new RefCountSubscriber(subscriber, connectable);
        const subscription = source.subscribe(refCounter);
        if (!refCounter.closed) {
            refCounter.connection = connectable.connect();
        }
        return subscription;
    }
}
class RefCountSubscriber extends Subscriber {
    constructor(destination, connectable) {
        super(destination);
        this.connectable = connectable;
    }
    _unsubscribe() {
        const { connectable } = this;
        if (!connectable) {
            this.connection = null;
            return;
        }
        this.connectable = null;
        const refCount = connectable._refCount;
        if (refCount <= 0) {
            this.connection = null;
            return;
        }
        connectable._refCount = refCount - 1;
        if (refCount > 1) {
            this.connection = null;
            return;
        }
        ///
        // Compare the local RefCountSubscriber's connection Subscription to the
        // connection Subscription on the shared ConnectableObservable. In cases
        // where the ConnectableObservable source synchronously emits values, and
        // the RefCountSubscriber's downstream Observers synchronously unsubscribe,
        // execution continues to here before the RefCountOperator has a chance to
        // supply the RefCountSubscriber with the shared connection Subscription.
        // For example:
        // ```
        // Observable.range(0, 10)
        //   .publish()
        //   .refCount()
        //   .take(5)
        //   .subscribe();
        // ```
        // In order to account for this case, RefCountSubscriber should only dispose
        // the ConnectableObservable's shared connection Subscription if the
        // connection Subscription exists, *and* either:
        //   a. RefCountSubscriber doesn't have a reference to the shared connection
        //      Subscription yet, or,
        //   b. RefCountSubscriber's connection Subscription reference is identical
        //      to the shared connection Subscription
        ///
        const { connection } = this;
        const sharedConnection = connectable._connection;
        this.connection = null;
        if (sharedConnection && (!connection || sharedConnection === connection)) {
            sharedConnection.unsubscribe();
        }
    }
}
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