`addHasCellListener`

The addHasCellListener method registers a listener function with the Store that will be called when a Cell is added to or removed from the Store.

addHasCellListener(
  tableId: IdOrNull,
  rowId: IdOrNull,
  cellId: IdOrNull,
  listener: HasCellListener<Store>,
  mutator?: boolean,
): string

	Type	Description
`tableId`	`IdOrNull`	The `Id` of the `Table` to listen to, or `null` as a wildcard.
`rowId`	`IdOrNull`	The `Id` of the `Row` to listen to, or `null` as a wildcard.
`cellId`	`IdOrNull`	The `Id` of the `Cell` to listen to, or `null` as a wildcard.
`listener`	`HasCellListener<Store>`	The function that will be called whenever the matching `Cell` is added or removed.
`mutator?`	`boolean`	An optional boolean that indicates that the listener mutates `Store` data.
returns	`string`	A unique `Id` for the listener that can later be used to call it explicitly, or to remove it.

The provided listener is a HasCellListener function, and will be called with a reference to the Store, the Id of the Table that changed, the Id of the Row that changed, and the Id of the Cell that changed. It is also given a flag to indicate whether the Cell now exists (having not done previously), or does not (having done so previously).

You can either listen to a single Cell being added or removed (by specifying the Table Id, Row Id, and Cell Id as the method's first three parameters) or changes to any Cell (by providing null wildcards).

All, some, or none of the tableId, rowId, and cellId parameters can be wildcarded with null. You can listen to a specific Cell in a specific Row in a specific Table, any Cell in any Row in any Table, for example - or every other combination of wildcards.

Use the optional mutator parameter to indicate that there is code in the listener that will mutate Store data. If set to false (or omitted), such mutations will be silently ignored. All relevant mutator listeners (with this flag set to true) are called before any non-mutator listeners (since the latter may become relevant due to changes made in the former). The changes made by mutator listeners do not fire other mutating listeners, though they will fire non-mutator listeners.

Examples

This example registers a listener that responds to a specific Cell being added or removed.

import {createStore} from 'tinybase';

const store = createStore().setTables({
  pets: {fido: {species: 'dog', color: 'brown'}},
});
const listenerId = store.addHasCellListener(
  'pets',
  'fido',
  'color',
  (store, tableId, rowId, cellId, hasCell) => {
    console.log(
      'color cell in fido row in pets table ' +
        (hasCell ? 'added' : 'removed'),
    );
  },
);

store.delCell('pets', 'fido', 'color');
// -> 'color cell in fido row in pets table removed'

store.setCell('pets', 'fido', 'color', 'walnut');
// -> 'color cell in fido row in pets table added'

store.delListener(listenerId);

This example registers a listener that responds to any Cell being added or removed.

import {createStore} from 'tinybase';

const store = createStore().setTables({
  pets: {fido: {species: 'dog', color: 'brown'}},
});
const listenerId = store.addHasCellListener(
  null,
  null,
  null,
  (store, tableId, rowId, cellId, hasCell) => {
    console.log(
      `${cellId} cell in ${rowId} row in ${tableId} table ` +
        (hasCell ? 'added' : 'removed'),
    );
  },
);

store.delCell('pets', 'fido', 'color');
// -> 'color cell in fido row in pets table removed'
store.setTable('species', {dog: {price: 5}});
// -> 'price cell in dog row in species table added'

store.delListener(listenerId);

This example registers a listener that responds to a specific Cell being added or removed, and which also mutates the Store itself.

import {createStore} from 'tinybase';

const store = createStore().setTables({
  pets: {fido: {species: 'dog', color: 'brown'}},
});
const listenerId = store.addHasCellListener(
  'pets',
  'fido',
  'color',
  (store, tableId, rowId, cellId) =>
    store.setCell('meta', 'update', `${tableId}_${rowId}_${cellId}`, true),
  true,
);

store.delCell('pets', 'fido', 'color');
console.log(store.getTable('meta'));
// -> {update: {pets_fido_color: true}}

store.delListener(listenerId);

Since

v4.4.0