export declare type Nullable<T> = T | null | undefined;
export interface SubscriptionLike {
    unsubscribe(): void;
}
/**
 * Subscription sink that holds Observable subscriptions
 * until you call unsubscribe on it in ngOnDestroy.
 */
export declare class SubSink {
    protected _subs: Nullable<SubscriptionLike>[];
    /**
     * Subscription sink that holds Observable subscriptions
     * until you call unsubscribe on it in ngOnDestroy.
     *
     * @example
     * In Angular:
     * ```
     *   private subs = new SubSink();
     *   ...
     *   this.subs.sink = observable$.subscribe(...)
     *   this.subs.add(observable$.subscribe(...));
     *   ...
     *   ngOnDestroy() {
     *     this.subs.unsubscribe();
     *   }
     * ```
     */
    constructor();
    /**
     * Add subscriptions to the tracked subscriptions
     * @example
     *  this.subs.add(observable$.subscribe(...));
     */
    add(...subscriptions: Nullable<SubscriptionLike>[]): void;
    /**
     * Assign subscription to this sink to add it to the tracked subscriptions
     * @example
     *  this.subs.sink = observable$.subscribe(...);
     */
    set sink(subscription: Nullable<SubscriptionLike>);
    /**
     * Unsubscribe to all subscriptions in ngOnDestroy()
     * @example
     *   ngOnDestroy() {
     *     this.subs.unsubscribe();
     *   }
     */
    unsubscribe(): void;
}