58 lines
1.5 KiB
TypeScript
58 lines
1.5 KiB
TypeScript
   
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/*
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Copyright 2025 New Vector Ltd.
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SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
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Please see LICENSE files in the repository root for full details.
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*/
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/**
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* Utility class for view models to manage suscriptions to their updates
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*/
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export class ViewModelSubscriptions {
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private listeners = new Set<() => void>();
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/**
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* @param updateSubscription A function called whenever a listener is added or removed.
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*/
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public constructor(
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private subscribeCallback: () => void,
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private unsubscribeCallback: () => void,
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) {}
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/**
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* Subscribe to changes in the view model.
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* @param listener Will be called whenever the snapshot changes.
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* @returns A function to unsubscribe from the view model updates.
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*/
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public add = (listener: () => void): (() => void) => {
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this.listeners.add(listener);
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if (this.listeners.size === 1) {
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this.subscribeCallback();
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}
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return () => {
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this.listeners.delete(listener);
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if (this.listeners.size === 0) {
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this.unsubscribeCallback();
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}
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};
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};
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/**
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* Emit an update to all subscribed listeners.
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*/
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public emit(): void {
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for (const listener of this.listeners) {
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listener();
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}
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}
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/**
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* Get the number of listeners currently subscribed to updates.
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* @returns The number of listeners.
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*/
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public listenerCount(): number {
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return this.listeners.size;
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}
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}
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