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addWillSetCellCallback

The addWillSetCellCallback method registers a WillSetCellCallback that will be called before any Cell is set in the Store.

addWillSetCellCallback(callback: WillSetCellCallback): Middleware
TypeDescription
callbackWillSetCellCallback

The WillSetCellCallback to register.

returnsMiddleware

A reference to the Middleware object, for chaining.

The callback can transform the Cell value or return undefined to prevent the write. Multiple callbacks can be registered and they are called sequentially, each receiving the (possibly transformed) value from the previous callback.

Examples

This example registers a callback that upper-cases string Cell values in the 'pets' table.

import {createMiddleware, createStore} from 'tinybase';

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

middleware.addWillSetCellCallback((tableId, rowId, cellId, cell) =>
  tableId === 'pets' && typeof cell === 'string'
    ? cell.toUpperCase()
    : cell,
);

store.setCell('pets', 'fido', 'species', 'dog');
console.log(store.getCell('pets', 'fido', 'species'));
// -> 'DOG'

middleware.destroy();

This example registers a callback that prevents writes to the 'species' table.

import {createMiddleware, createStore} from 'tinybase';

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

middleware.addWillSetCellCallback((tableId, _rowId, _cellId, cell) =>
  tableId === 'species' ? undefined : cell,
);

store.setCell('species', 'dog', 'legs', 4);
console.log(store.getTables());
// -> {}

middleware.destroy();

Since

v8.0.0