Storex

Storex is a frontend store with state management handled on the backend. It allows you to update the store state both from the frontend and backend, with all communication occurring over WebSocket.

Important: Storex is currently under active development. We encourage you to report any issues or submit feature requests here.

Why Storex?

Features

• Efficient state management: Only the differences (diffs) in the store state are sent with each mutation, minimizing data transfer.
• Real-time updates: State changes are immediately reflected across all connected clients via WebSocket communication.
• Backend-driven state: Storex allows both the frontend and backend to update the store state seamlessly.
• Lightweight and fast: Designed for minimal overhead, ensuring rapid state updates and communication.

Key Differences from Phoenix LiveView

Phoenix LiveView is a powerful tool for building rich, interactive web applications without writing custom JavaScript. However, as your application grows, managing complex client-side state across multiple LiveViews or components can become challenging. This is where Storex comes in.

• Client-Side State Management: While Phoenix LiveView handles server-side rendering and event handling, Storex focuses on managing state on the client side. It allows you to keep your client-side state in sync with the server, but with more flexibility in how that state is stored, updated, and accessed.
• Decoupled State Logic: Storex decouples state management from the LiveView itself, enabling you to manage state across multiple components or even across the entire application. This contrasts with LiveView, where state is typically tied to a specific LiveView process.
• Predictable State Updates: Storex follows a predictable, unidirectional data flow similar to Redux. This makes it easier to reason about state changes and debug issues, especially in complex applications.
• Extensibility: Storex is designed to be highly extensible, allowing you to integrate it with other tools and libraries in the Elixir ecosystem. You can also define custom middleware to handle side effects, logging, or other tasks.

For an overview of Storex in action, check out the example provided here.

Basic usage

Installation

Add storex to deps in mix.exs:

defp deps do
  [{:storex, "~> 0.5.0"}]
end

Also you need to add storex to package.json dependencies:

{
  "storex": "file:../deps/storex",
}

Add storex websocket handler

You need to add handler Storex.Handler.Plug or Storex.Handler.Cowboy.

Phoenix:

defmodule YourAppWeb.Endpoint do
  use Phoenix.Endpoint, otp_app: :your_app

  plug Storex.Plug, path: "/storex"

  # ...
end

Cowboy:

:cowboy_router.compile([
  {:_, [
    # ...
    {"/storex", Storex.Handler.Cowboy, []},
    # ...
  ]}
])

[!IMPORTANT] Cowboy doesn’t support the Node.js (HTTP Only) connector

Create store

To create a store you need to create new elixir module with init/2 which is called when a page is loaded, every time websocket is connected it generates session_id and passes it as the first argument, params are from Javascript store declaration. init/2 callback need to return one of this tuples:

• {:ok, state} - for initial state
• {:ok, state, key} - for initial state with key which can be used as selector for future mutations
• {:error, reason} - to send error message to frontend on initialization

Next, you can declare mutation/5 where the first argument is mutation name, second is data passed to mutation, next two params are same like in init/2, the last one is the current state of the store.

defmodule ExampleApp.Store.Counter do
  use Storex.Store

  def init(session_id, params) do
    {:ok, 0}
  end

  # `increase` is mutation name, `data` is payload from front-end, `session_id` is current session id of connecton, `initial_params` with which store was initialized, `state` is store current state.
  def mutation("increase", _data, _session_id, _initial_params, state) do
    state = state + 1

    {:noreply, state}
  end

  def mutation("decrease", _data, _session_id, _initial_params, state) do
    state = state - 1

    {:reply, "message", state}
  end

  def mutation("set", [number], _session_id, _initial_params, state) do
    {:noreply, number}
  end
end

Connect to store

You have to connect the newly created store with a frontend side to be able to synchronise the state: params are passed as second argument in store init/2 and as third in mutation/5. You can subscribe to changes inside store state by passing option subscribe with function as a value.

import useStorex from 'storex'

const store = useStorex({
  store: 'ExampleApp.Store.Counter',
  params: {}
})

Mutate store

You can mutate store from javascript with store instance:

store.commit("increase")
store.commit("decrease").then((response) => {
  response // Reply from elixir
})
store.commit("set", 10)

Or directly from elixir:

Storex.mutate(store, "increase", [])
Storex.mutate(store, "set", [10])
Storex.mutate(key, store, "increase", [])
Storex.mutate(key, store, "set", [10])

Subscribe to store changes

You can subscribe to store state changes in javascript with function subscribe:

store.subscribe((state) => {
  const state = state
})

You can also subscribe to events after store is created:

store.onConnected(() => {
  console.log('connected')
})

store.onError((error) => {
  console.log('error', error)
})

store.onDisconnected((closeEvent) => {
  console.log('disconnected', closeEvent)
})

Connectors

The default export of useStorex uses WebSocket connections only, you can extend it by using custom connector.

Websocket

import { prepare, socketConnector } from 'storex';

const connector = socketConnector({ address: 'wss://myapi.com/storex' });
const { useStorex } = prepare({ /* global params */ }, connector);

const myStore = useStorex<MyStateType>({
  store: &#39;myStoreName&#39;,
  params: { /* store-specific params */ }
});

Node.js (HTTP Only)

Node.js connector require Node.js installed on server which running application

import { prepare, httpConnector } from 'storex';

const connector = httpConnector({ address: 'http://myapi.com/storex' });
const { useStorex } = prepare({}, connector);

const myStore = useStorex<MyStateType>({
  store: &#39;myStoreName&#39;,
  params: { /* store-specific params */ }
});

// Subscribe to state changes
myStore.subscribe((state) => {
  console.log(&#39;New state:&#39;, state);
});

// Handle errors
myStore.onError((error) => {
  console.error(&#39;An error occurred:&#39;, error);
});

[!IMPORTANT] Mutations are not supported in HTTP mode myStore.commit() will not work as expected

Configuration

Session id generation library

You can change library which generate session id for stores. Module needs to have generate/0 method.

config :storex, :session_id_library, Ecto.UUID

Default params

You can set default params for all stores when preparing the Storex instance. These params will be passed to each store.

const { useStorex } = prepare({ jwt: 'someJWT' }, connector);

Custom store address

You can specify a custom address when creating the connector:

const connector = socketConnector({ address: 'wss://myapi.com/storex' });
// OR
const connector = httpConnector({ address: 'http://myapi.com/storex' });