loaderclass.md

Loader Class

The Loader Class helps you create an MMKV Instance. Once the instance is loaded, you can then use it to read and write data in database. It follows a builder pattern. You need to tell the Loader class everything about the MMKV Instance you want to create and then finally call initialize to create and get the instance.

Create a Loader

You can simply create a new Loader as follows:

import { MMKVLoader } from "react-native-mmkv-storage";

const MMKV = new MMKVLoader();

initialize

Initialize the MMKV Instance with the selected properties. Returns an MMKV Instance that you can use.

import { MMKVLoader } from "react-native-mmkv-storage";

const MMKV = new MMKVLoader();

MMKV.initialize();

Returns: API

withInstanceID

Specifies that the MMKV Instance should be created with the given ID. This way multiple intances can be created.

Arguments

Name	Type
ID	String

import { MMKVLoader } from "react-native-mmkv-storage";

const MMKV = new MMKVLoader();

MMKV = MMKV.withInstanceID("mmkvInstanceWithID");

Returns: this;

withEncryption

Encrypt the MMKV instance on initialization. By default the library generates a strong password and stores it in Keychain on iOS and Android Keystore in Android.

Arguments

Name	Type
ID	String

import { MMKVLoader } from "react-native-mmkv-storage";

const MMKV = new MMKVLoader();

MMKV = MMKV.withEncryption();

Returns: this;

encryptWithCustomKey

You can also specify your own password to encrypt the storage.

Arguments

Name	Required	Type	Description
cryptKey	yes	String	Password to encrypt the storage
secureKeyStorage	no	boolean	Set to true of you want the library to store the password securely
alias	no	String	You can provide a custom alias for storage of password, by default instanceID is used

import { MMKVLoader } from "react-native-mmkv-storage";

const MMKV = new MMKVLoader();

MMKV = MMKV.withEncryption().encryptWithCustomKey("encryptionKey");

Returns: this;

setProcessingMode

You can choose between single process or multiprocess MMKV instance.

Arguments

Name	Required	Type	Description
mode	yes	ProcessingModes	Select the processing mode

import { MMKVLoader,ProcessingModes } from "react-native-mmkv-storage";

const MMKV = new MMKVLoader();

MMKV = MMKV.setProcessingMode( ProcessingModes.SINGLE_PROCESS); // OR MMKVStorage.MODES.MULTI_PROCESS

setAccessibleMode (iOS only)

Choose the accessibility mode for secure key storage (IOS ONLY);

Arguments

Name	Required	Type	Description
accessible	yes	IOSAccessibleStates	Choose the accessibility mode

import { MMKVLoader, IOSAccessibleStates } from "react-native-mmkv-storage";

const MMKV = new MMKVLoader();

MMKV = MMKV.setAccessibleMode(IOSAccessibleStates.WHEN_UNLOCKED);

type IOSAccessibleStates = {
  WHEN_UNLOCKED: string;
  AFTER_FIRST_UNLOCK: string;
  /** @deprecated in iOS 16+ */
  ALWAYS: string;
  WHEN_PASSCODE_SET_THIS_DEVICE_ONLY: string;
  WHEN_UNLOCKED_THIS_DEVICE_ONLY: string;
  AFTER_FIRST_UNLOCK_THIS_DEVICE_ONLY: string;
  /** @deprecated in iOS 16+ */
  ALWAYS_THIS_DEVICE_ONLY: string;
};

Returns: this;

withServiceName (iOS only)

Sets the kSecAttrService option for secure key storage (IOS ONLY);

Arguments

Name	Required	Type	Description
serviceName	yes	String	The service name

import { MMKVLoader } from "react-native-mmkv-storage";

const MMKV = new MMKVLoader();

MMKV = MMKV.withServiceName('com.MMKV.example');

Returns: this;

Putting it together

Now you know about the loader class, lets create a MMKV Instance with an ID.

import { MMKVLoader } from "react-native-mmkv-storage";

MMKV = new MMKVLoader().
.withInstanceID('mmkvInstanceID')
.setProcessingMode(MMKVStorage.MODES.MULTI_PROCESS)
.withEncryption()
.encryptWithCustomKey('encryptionKey',true, 'customAlias')
.initialize()

// then use it


  await MMKV.setStringAsync("string", "string");

  let string = await MMKV.getStringAsync("string");