stack/packages/mosaic/framework/skills/vueuse-functions/references/useMemoize.md

category

category
Utilities

useMemoize

Cache results of functions depending on arguments and keep it reactive. It can also be used for asynchronous functions and will reuse existing promises to avoid fetching the same data at the same time.

::: tip The results are not cleared automatically. Call clear() in case you no longer need the results or use own caching mechanism to avoid memory leaks. :::

Usage

import { useMemoize } from '@vueuse/core';

const getUser = useMemoize(
  async (userId: number): Promise<UserData> =>
    axios.get(`users/${userId}`).then(({ data }) => data),
);

const user1 = await getUser(1); // Request users/1
const user2 = await getUser(2); // Request users/2
// ...
const user1 = await getUser(1); // Retrieve from cache

// ...
const user1 = await getUser.load(1); // Request users/1

// ...
getUser.delete(1); // Delete cache from user 1
getUser.clear(); // Clear full cache

Combine with computed or computedAsync to achieve reactivity:

import { computedAsync, useMemoize } from '@vueuse/core';

const getUser = useMemoize(
  async (userId: number): Promise<UserData> =>
    axios.get(`users/${userId}`).then(({ data }) => data),
);
// ---cut---
const user1 = computedAsync(() => getUser(1));
// ...
await getUser.load(1); // Will also update user1

Resolving cache key

The key for caching is determined by the arguments given to the function and will be serialized by default with JSON.stringify. This will allow equal objects to receive the same cache key. In case you want to customize the key you can pass getKey

::: warning Performance Consideration Using JSON.stringify as the default key generator can be slow for large or complex objects. For better performance with complex arguments, it's highly recommended to provide a custom getKey function that generates keys based on primitive values or unique identifiers. :::

Basic Example

import { useMemoize } from '@vueuse/core';
// ---cut---
const getUser = useMemoize(
  async (userId: number, headers: AxiosRequestHeaders): Promise<UserData> =>
    axios.get(`users/${userId}`, { headers }).then(({ data }) => data),
  {
    // Use only userId to get/set cache and ignore headers
    getKey: (userId, headers) => userId,
  },
);

Customize cache mechanism

By default, the results are cached within a Map. You can implement your own mechanism by passing cache as options with following structure:

export interface MemoizeCache<Key, Value> {
  /**
   * Get value for key
   */
  get: (key: Key) => Value | undefined;
  /**
   * Set value for key
   */
  set: (key: Key, value: Value) => void;
  /**
   * Return flag if key exists
   */
  has: (key: Key) => boolean;
  /**
   * Delete value for key
   */
  delete: (key: Key) => void;
  /**
   * Clear cache
   */
  clear: () => void;
}

Type Declarations

type CacheKey = any;
/**
 * Custom memoize cache handler
 */
export interface UseMemoizeCache<Key, Value> {
  /**
   * Get value for key
   */
  get: (key: Key) => Value | undefined;
  /**
   * Set value for key
   */
  set: (key: Key, value: Value) => void;
  /**
   * Return flag if key exists
   */
  has: (key: Key) => boolean;
  /**
   * Delete value for key
   */
  delete: (key: Key) => void;
  /**
   * Clear cache
   */
  clear: () => void;
}
/**
 * Memoized function
 */
export interface UseMemoizeReturn<Result, Args extends unknown[]> {
  /**
   * Get result from cache or call memoized function
   */
  (...args: Args): Result;
  /**
   * Call memoized function and update cache
   */
  load: (...args: Args) => Result;
  /**
   * Delete cache of given arguments
   */
  delete: (...args: Args) => void;
  /**
   * Clear cache
   */
  clear: () => void;
  /**
   * Generate cache key for given arguments
   */
  generateKey: (...args: Args) => CacheKey;
  /**
   * Cache container
   */
  cache: UseMemoizeCache<CacheKey, Result>;
}
export interface UseMemoizeOptions<Result, Args extends unknown[]> {
  getKey?: (...args: Args) => string | number;
  cache?: UseMemoizeCache<CacheKey, Result>;
}
/**
 * Reactive function result cache based on arguments
 *
 * @__NO_SIDE_EFFECTS__
 */
export declare function useMemoize<Result, Args extends unknown[]>(
  resolver: (...args: Args) => Result,
  options?: UseMemoizeOptions<Result, Args>,
): UseMemoizeReturn<Result, Args>;