MMKV
MMKV is an efficient, small mobile key-value storage framework developed by WeChat.
See Tencent/MMKV for more information
react-native-mmkv is a library that allows you to use MMKV inside your React Native applications.
Features
- Get and set strings, booleans and numbers
- Fully synchronous calls, no async/await, no Promises, no Bridge.
- High performance because everything is written in C++ (even the JS functions have C++ bodies!)
- ~30x faster than AsyncStorage
- Uses JSI instead of the "old" Bridge
Fun fact: since all the JS functions have C++ implementations, you can also directly call them in reanimated worklets, Vision Camera frame processors or custom threads using react-native-multithreading.
Benchmark
![](https://raw.githubusercontent.com/matheusmatos/react-native-mmkv/master/./img/benchmark_1000_get.png)
AsyncStorage vs MMKV: Reading a value from Storage 1000 times.
Measured in milliseconds on an iPhone 8, lower is better.
Installation
npm install react-native-mmkv
iOS
iOS installation is automatic, just run:
cd ios && pod install
Android
To correctly initialize MMKV on Android, please follow the Installation guide.
Usage
Set
import { MMKV } from 'react-native-mmkv';
MMKV.set('user.name', 'Marc')
MMKV.set('user.age', 20)
MMKV.set('is-mmkv-fast-asf', true)
Get
import { MMKV } from 'react-native-mmkv';
const username = MMKV.getString('user.name') // 'Marc'
const age = MMKV.getNumber('user.age') // 20
const isMmkvFastAsf = MMKV.getBoolean('is-mmkv-fast-asf') // true
Delete
import { MMKV } from 'react-native-mmkv';
MMKV.delete('user.name')
Get all keys
import { MMKV } from 'react-native-mmkv';
const keys = MMKV.getAllKeys() // ['user.name', 'user.age', 'is-mmkv-fast-asf']
Objects
import { MMKV } from 'react-native-mmkv';
const user = {
username: 'Marc',
age: 20
}
MMKV.set('user', JSON.stringify(user))
const jsonUser = MMKV.getString('user') // { 'username': 'Marc', 'age': 20 }
const userObject = JSON.parse(jsonUser)
Delete all keys
import { MMKV } from 'react-native-mmkv';
MMKV.deleteAllKeys()
Migrate from AsyncStorage
See #52 for instructions on how to safely migrate your existing AsyncStorage database to MMKV.
Limitations
As the library uses JSI for synchronous native methods access, remote debugging (e.g. with Chrome) is no longer possible. Instead, you should use Flipper.
redux-persist
If you want to use MMKV with redux-persist, create the following storage
object:
import { MMKV } from "react-native-mmkv";
import { Storage } from "redux-persist";
// Unfortunately redux-persist expects Promises,
// so we have to wrap our sync calls with Promise resolvers/rejecters
export const storage: Storage = {
setItem: (key: string, value: string): Promise<boolean> => {
MMKV.set(key, value);
return Promise.resolve(true);
},
getItem: (key: string): Promise<string> => {
const value = MMKV.getString(key);
return Promise.resolve(value);
},
removeItem: (key: string): Promise<void> => {
MMKV.delete(key);
return Promise.resolve();
},
};
mobx-persist-store
If you want to use MMKV with mobx-persist-store, create the following storage
object:
import { MMKV } from 'react-native-mmkv';
import { configurePersistable } from 'mobx-persist-store';
configurePersistable({
storage: {
setItem: (key, data) => MMKV.set(key, data),
getItem: (key) => MMKV.getString(key),
removeItem: (key) => MMKV.delete(key),
},
});
For more information, check out kanzitelli/rnn-starter.
Contributing
See the contributing guide to learn how to contribute to the repository and the development workflow.
License
MIT