Async Storage Middleware

A Galena middleware for persisting units of State with Async Storage.

Getting Started

Installation

npm install --save @figliolia/galena-async-storage
# or
yarn add @figliolia/galena-async-storage

Basic Usage

import { State } from "@figliolia/galena";
import { AsyncStorageMiddleware } from "@figliolia/galena-async-storage";
import AsyncStorage from "@react-native-async-storage/async-storage";

const UserState = new State("User", {
  token: "",
  username: ""
});

void AsyncStorage.getItem("User").then(savedState => {
  if(savedState) {
    // Initialize User State from async storage
    UserState.update(state => {
      state.token = savedState.token;
      state.username = savedState.username;
    });
  }
  // Persist all future state mutations using AsyncStorageMiddleware
  UserState.registerMiddleware(new AsyncStorageMiddleware());
});

Persisting State Mutations

Once the AsyncStorageMiddleware() is registered on your state, each call to State.update(), State.backgroundUpdate(), and State.priorityUpdate() will persist the latest mutation into AsyncStorage. Each entry's key will be equal to State.name.

Factories for Persisted Galena State

In production, you may find yourself with several units of State requiring AsyncStorage. If using Galena instances, applying this middleware to all unit's of State is as easy as calling:

import { Galena } from "@figliolia/galena";
import { AsyncStorageMiddleware } from "@figliolia/galena-async-storage";

export const AppState = new Galena([
  new AsyncStorageMiddleware()
]);

const MyState = AppState.composeState("My State", {
  token: "",
  username: ""
});
// MyState.middleware = [new AsyncStorageMiddleware()];

However, if you're using Island Architecture and require several AsyncStorage-persisted units of State, a factory can be created for automatically applying the AsyncStorageMiddleware

import { State, type Middleware } from "@figliolia/galena";
import { AsyncStorageMiddleware } from "@figliolia/galena-async-storage";

export const createPersistedState = <T>(
  name: string, 
  initialState: T, 
  middleware: [new AsyncStorageMiddleware()]
) => {
  const state = new State<T>(name, initialState);
  state.registerMiddleware(...middleware);
  return state;
}