491f0cd08a
* Copyright headers 1 * Licence headers 2 * Copyright Headers 3 * Copyright Headers 4 * Copyright Headers 5 * Copyright Headers 6 * Copyright headers 7 * Add copyright headers for html and config file * Replace license files and update package.json * Update with CLA * lint
48 lines
1.1 KiB
TypeScript
48 lines
1.1 KiB
TypeScript
/*
|
|
Copyright 2024 New Vector Ltd.
|
|
Copyright 2021 The Matrix.org Foundation C.I.C.
|
|
|
|
SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only
|
|
Please see LICENSE files in the repository root for full details.
|
|
*/
|
|
|
|
/**
|
|
* Utility class for lazily getting a variable.
|
|
*/
|
|
export class LazyValue<T> {
|
|
private val?: T;
|
|
private prom?: Promise<T>;
|
|
private done = false;
|
|
|
|
public constructor(private getFn: () => Promise<T>) {}
|
|
|
|
/**
|
|
* Whether or not a cached value is present.
|
|
*/
|
|
public get present(): boolean {
|
|
// we use a tracking variable just in case the final value is falsy
|
|
return this.done;
|
|
}
|
|
|
|
/**
|
|
* Gets the value without invoking a get. May be undefined until the
|
|
* value is fetched properly.
|
|
*/
|
|
public get cachedValue(): T | undefined {
|
|
return this.val;
|
|
}
|
|
|
|
/**
|
|
* Gets a promise which resolves to the value, eventually.
|
|
*/
|
|
public get value(): Promise<T> {
|
|
if (this.prom) return this.prom;
|
|
this.prom = this.getFn();
|
|
|
|
return this.prom.then((v) => {
|
|
this.val = v;
|
|
this.done = true;
|
|
return v;
|
|
});
|
|
}
|
|
}
|