Skip to main content

Tracking models changes

What you'll learn
  • Tracking a model's instance changes
  • Creating snapshots of a model's instance
  • Restoring snapshots of a model's instance

Foscia will track changes over your instances properties (IDs, attributes or relations) throughout their existence.

Each time you send/fetch an instance to/from your data source, your instance's properties will be synced in an "original" snapshot.

This original snapshot allows you to check if some properties have changed since last synchronization.

Taking a snapshot​

You can take a snapshot of an instance at any time using takeSnapshot. This is done automatically every time you send/fetch an instance to/form your data source, and the created snapshot is saved into the $original properties of your instance.

import { takeSnapshot } from 'foscia/core';

const myPostSnapshot = takeSnapshot(myPost);

Checking for changes​

To check for changes between two snapshots, you can use compareSnapshots. To check for changes between an instance and its original snapshot, you can use changed (this will automatically take a new snapshot and compare against it).

import { changed, compareSnapshots, takeSnapshot } from 'foscia/core';

// True if any properties changed or instance does exists now.
changed(myPost);
// False in the same case as above.
compareSnapshots(takeSnapshot(myPost), myPost.$original);

// True only if title has changed.
changed(myPost, ['title']);
// False in the same case as above.
compareSnapshots(takeSnapshot(myPost), myPost.$original, ['title']);

Syncing changes​

You can mark your instance as synced any time using markSynced. Just like other helper functions, you can affect only specific properties.

import { markSynced } from 'foscia/core';

// Mark all properties synced in $original snapshot.
markSynced(myPost);
// Mark the title synced on $original snapshot.
markSynced(myPost, ['title']);

Restoring changes​

You can restore a snapshot on your model as synced any time using restore and restoreSnapshot. Just like other helper functions, you can affect only specific properties.

import { restore, restoreSnapshot } from 'foscia/core';

// Restore whole state.
restore(myPost);
// Equivalent with `restoreSnapshot`
restoreSnapshot(myPost, myPost.$original);
// Restore title property only.
restore(myPost, ['title']);
// Equivalent with `restoreSnapshot`
restoreSnapshot(myPost, myPost.$original, ['title']);