@statesync/mobx

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@statesync/mobx / createMobXSnapshotApplier

Function: createMobXSnapshotApplier()

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

Defined in: mobx.ts:264

Creates a SnapshotApplier that applies incoming snapshots into a MobX observable store by mutating it in place.

This is a framework adapter: it only focuses on how to apply a snapshot into a concrete MobX 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 mutates the MobX observable in place by assigning or deleting individual properties inside a single runInAction call (when provided).
4. MobX's reactivity system automatically notifies all subscribers (autorun, reaction, observer()) of the changed properties.

Framework-specific note: The store reference is never replaced. All mutations are applied directly to the existing observable object so that autorun, reaction, and observer() consumers continue to work without any re-wiring.

Type Parameters

Type Parameter	Default type	Description
State extends Record<string, unknown>	-	The shape of the MobX observable'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	State	The MobX observable (or any object satisfying MobXStoreLike) to apply snapshots into.
options	MobXSnapshotApplierOptions<State, Data>	Configuration for apply mode, key filtering, data mapping, runInAction wrapping, and strict validation.

Returns

SnapshotApplier<Data>

A SnapshotApplier whose apply method writes snapshot data into the MobX store.

Throws

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

Examples

import { makeAutoObservable, runInAction } from 'mobx';
import { createMobXSnapshotApplier } from '@statesync/mobx';
import { createRevisionSync } from '@statesync/core';

class ProfileStore {
  name = '';
  email = '';
  constructor() { makeAutoObservable(this); }
}

const store = new ProfileStore();
const applier = createMobXSnapshotApplier(store, { runInAction });

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

const applier = createMobXSnapshotApplier(store, {
  mode: 'replace',
  runInAction,
  omitKeys: ['isMenuOpen'],
});