export type Subscriber<T> = (message: T) => void;
export type Unsubscribe = () => void;
export declare class Subject<T> {
    #private;
    constructor();
    /**
     * @desc Returns the number of subscribers
     */
    get size(): number;
    /**
     * @desc Subscribes to a subject
     * @param observer - The observer to subscribe
     */
    subscribe(observer: Subscriber<T>): () => boolean;
    /**
     * @desc Publishes a message to all subscribers
     * @param message - The message to publish
     */
    publish(message: T): void;
}