@statesync/redux

---

@statesync/redux / createReduxSnapshotApplier

Function: createReduxSnapshotApplier()

function createReduxSnapshotApplier<State, Data>(store, options): SnapshotApplier<Data>;

Defined in: redux.ts:388

Creates a SnapshotApplier that applies incoming snapshots into a Redux store by dispatching a SnapshotAppliedAction.

This is a framework adapter: it only focuses on how to apply a snapshot into a concrete Redux state container. It does not fetch snapshots and does not subscribe to invalidation events — those concerns belong to the sync engine (@statesync/core).

How state updates propagate:

1. The sync engine receives an invalidation event and fetches a new snapshot from the server.
2. The engine calls applier.apply(envelope) with the snapshot data.
3. This adapter maps the snapshot data to a state patch (via toState), filters keys (via pickKeys / omitKeys), and dispatches a SnapshotAppliedAction to the Redux store.
4. A reducer (either wrapped with withSnapshotHandling or handling SNAPSHOT_ACTION_TYPE manually) processes the action and produces the next state.

Key difference from other adapters: Redux state can only be updated via dispatching actions through reducers. This adapter dispatches a well-defined action instead of mutating state directly.

Type Parameters

Type Parameter	Default type	Description
State extends Record<string, unknown>	-	The shape of the Redux store's state object.
Data	State	The snapshot payload type received from the sync engine. Defaults to State when the snapshot data matches the store shape.

Parameters

Parameter	Type	Description
store	ReduxStoreLike<State>	The Redux store (or any object satisfying ReduxStoreLike) to apply snapshots into.
options	ReduxSnapshotApplierOptions<State, Data>	Configuration for apply mode, key filtering, data mapping, and strict validation. See ReduxSnapshotApplierOptions.

Returns

SnapshotApplier<Data>

A SnapshotApplier whose apply method dispatches snapshot data into the Redux store.

Throws

When strict is true (the default) and toState returns a non-plain-object value.

Examples

import { configureStore } from '@reduxjs/toolkit';
import { createReduxSnapshotApplier, withSnapshotHandling } from '@statesync/redux';
import { createRevisionSync } from '@statesync/core';

const store = configureStore({
  reducer: withSnapshotHandling(rootReducer),
});

const applier = createReduxSnapshotApplier(store);

const sync = createRevisionSync({
  topic: 'user-profile',
  subscriber: mySubscriber,
  provider: mySnapshotProvider,
  applier,
});

const applier = createReduxSnapshotApplier(store, {
  mode: 'replace',
  omitKeys: ['localUiFlag'],
});

interface ApiResponse { user: { name: string; email: string } }

const applier = createReduxSnapshotApplier<ProfileState, ApiResponse>(
  store,
  { toState: (data) => data.user },
);