addWillApplyChangesCallback

The addWillApplyChangesCallback method registers a WillApplyChangesCallback that will be called before Changes are applied to the Store via the applyChanges method.

addWillApplyChangesCallback(callback: WillApplyChangesCallback): Middleware

This callback receives the Changes object and can return it (to allow), return a modified Changes object (to transform), or return undefined (to reject). Multiple callbacks can be registered and they are called sequentially, each receiving the output of the previous. If any callback returns undefined, all remaining callbacks are skipped and the changes are rejected.

This fires when applyChanges is called directly, or indirectly via applyMergeableChanges, setMergeableContent, or merge on a MergeableStore.

import {createMiddleware, createStore} from 'tinybase';

const store = createStore();
const middleware = createMiddleware(store);

middleware.addWillApplyChangesCallback(([changedTables, changedValues]) =>
  changedTables['secret'] != null
    ? undefined
    : [changedTables, changedValues, 1],
);

store.applyChanges([{pets: {fido: {species: 'dog'}}}, {}, 1]);
console.log(store.getRow('pets', 'fido'));
// -> {species: 'dog'}

store.applyChanges([{secret: {r1: {c1: 'v1'}}}, {}, 1]);
console.log(store.getTable('secret'));
// -> {}

middleware.destroy();