react-native-mmkv/lib/module/hooks.js

The fastest key/value storage for React Native. ~30x faster than AsyncStorage! Works on Android, iOS and Web.

import { useRef, useState, useMemo, useCallback, useEffect } from 'react';
import { MMKV } from './MMKV';
function isConfigurationEqual(left, right) {
  if (left == null || right == null) return left == null && right == null;
  return left.encryptionKey === right.encryptionKey && left.id === right.id && left.path === right.path;
}
let defaultInstance = null;
function getDefaultInstance() {
  if (defaultInstance == null) {
    defaultInstance = new MMKV();
  }
  return defaultInstance;
}

/**
 * Use the default, shared MMKV instance.
 */

export function useMMKV(configuration) {
  const instance = useRef();
  const lastConfiguration = useRef();
  if (configuration == null) return getDefaultInstance();
  if (instance.current == null || !isConfigurationEqual(lastConfiguration.current, configuration)) {
    lastConfiguration.current = configuration;
    instance.current = new MMKV(configuration);
  }
  return instance.current;
}
function createMMKVHook(getter) {
  return (key, instance) => {
    const mmkv = instance ?? getDefaultInstance();
    const [value, setValue] = useState(() => getter(mmkv, key));
    const valueRef = useRef(value);
    valueRef.current = value;

    // update value by user set
    const set = useCallback(v => {
      const newValue = typeof v === 'function' ? v(valueRef.current) : v;
      switch (typeof newValue) {
        case 'number':
        case 'string':
        case 'boolean':
          mmkv.set(key, newValue);
          break;
        case 'undefined':
          mmkv.delete(key);
          break;
        case 'object':
          if (newValue instanceof Uint8Array) {
            mmkv.set(key, newValue);
            break;
          } else {
            throw new Error(`MMKV: Type object (${newValue}) is not supported!`);
          }
        default:
          throw new Error(`MMKV: Type ${typeof newValue} is not supported!`);
      }
    }, [key, mmkv]);

    // update value if key or instance changes
    useEffect(() => {
      setValue(getter(mmkv, key));
    }, [key, mmkv]);

    // update value if it changes somewhere else (second hook, same key)
    useEffect(() => {
      const listener = mmkv.addOnValueChangedListener(changedKey => {
        if (changedKey === key) {
          setValue(getter(mmkv, key));
        }
      });
      return () => listener.remove();
    }, [key, mmkv]);
    return [value, set];
  };
}

/**
 * Use the string value of the given `key` from the given MMKV storage instance.
 *
 * If no instance is provided, a shared default instance will be used.
 *
 * @example
 * ```ts
 * const [username, setUsername] = useMMKVString("user.name")
 * ```
 */
export const useMMKVString = createMMKVHook((instance, key) => instance.getString(key));

/**
 * Use the number value of the given `key` from the given MMKV storage instance.
 *
 * If no instance is provided, a shared default instance will be used.
 *
 * @example
 * ```ts
 * const [age, setAge] = useMMKVNumber("user.age")
 * ```
 */
export const useMMKVNumber = createMMKVHook((instance, key) => instance.getNumber(key));
/**
 * Use the boolean value of the given `key` from the given MMKV storage instance.
 *
 * If no instance is provided, a shared default instance will be used.
 *
 * @example
 * ```ts
 * const [isPremiumAccount, setIsPremiumAccount] = useMMKVBoolean("user.isPremium")
 * ```
 */
export const useMMKVBoolean = createMMKVHook((instance, key) => instance.getBoolean(key));
/**
 * Use the buffer value (unsigned 8-bit (0-255)) of the given `key` from the given MMKV storage instance.
 *
 * If no instance is provided, a shared default instance will be used.
 *
 * @example
 * ```ts
 * const [privateKey, setPrivateKey] = useMMKVBuffer("user.privateKey")
 * ```
 */
export const useMMKVBuffer = createMMKVHook((instance, key) => instance.getBuffer(key));
/**
 * Use an object value of the given `key` from the given MMKV storage instance.
 *
 * If no instance is provided, a shared default instance will be used.
 *
 * The object will be serialized using `JSON`.
 *
 * @example
 * ```ts
 * const [user, setUser] = useMMKVObject<User>("user")
 * ```
 */
export function useMMKVObject(key, instance) {
  const [string, setString] = useMMKVString(key, instance);
  const value = useMemo(() => {
    if (string == null) return undefined;
    return JSON.parse(string);
  }, [string]);
  const setValue = useCallback(v => {
    if (v == null) {
      // Clear the Value
      setString(undefined);
    } else {
      // Store the Object as a serialized Value
      setString(JSON.stringify(v));
    }
  }, [setString]);
  return [value, setValue];
}

/**
 * Listen for changes in the given MMKV storage instance.
 * If no instance is passed, the default instance will be used.
 * @param valueChangedListener The function to call whenever a value inside the storage instance changes
 * @param instance The instance to listen to changes to (or the default instance)
 *
 * @example
 * ```ts
 * useMMKVListener((key) => {
 *   console.log(`Value for "${key}" changed!`)
 * })
 * ```
 */
export function useMMKVListener(valueChangedListener, instance) {
  const ref = useRef(valueChangedListener);
  ref.current = valueChangedListener;
  const mmkv = instance ?? getDefaultInstance();
  useEffect(() => {
    const listener = mmkv.addOnValueChangedListener(changedKey => {
      ref.current(changedKey);
    });
    return () => listener.remove();
  }, [mmkv]);
}
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