`addRowCountListener`

The addRowCountListener method registers a listener function with the Store that will be called whenever the count of Row objects in a Table change.

addRowCountListener(
  tableId: IdOrNull,
  listener: RowCountListener<Store>,
  mutator?: boolean,
): string

	Type	Description
`tableId`	`IdOrNull`	The `Id` of the `Table` to listen to, or `null` as a wildcard.
`listener`	`RowCountListener<Store>`	The function that will be called whenever the number of `Row` objects in the `Table` changes.
`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 RowCountListener function, and will be called with a reference to the Store, the Id of the Table that changed, and the number of Row objects in the Table.

You can either listen to a single Table (by specifying its Id as the method's first parameter) or changes to any Table (by providing a null wildcard).

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 change in the number of Row objects in a specific Table.

import {createStore} from 'tinybase';

const store = createStore().setTables({pets: {fido: {species: 'dog'}}});
const listenerId = store.addRowCountListener(
  'pets',
  (store, _tableId, count) => {
    console.log('Row count for pets table changed to ' + count);
  },
);

store.setRow('pets', 'felix', {species: 'cat'});
// -> 'Row count for pets table changed to 2'

store.delListener(listenerId);

This example registers a listener that responds to any change to a change in the number of Row objects of any Table.

import {createStore} from 'tinybase';

const store = createStore().setTables({pets: {fido: {species: 'dog'}}});
const listenerId = store.addRowCountListener(
  null,
  (store, tableId, count) => {
    console.log(`Row count for ${tableId} table changed to ${count}`);
  },
);

store.setRow('pets', 'felix', {species: 'cat'});
// -> 'Row count for pets table changed to 2'
store.setRow('species', 'dog', {price: 5});
// -> 'Row count for species table changed to 1'

store.delListener(listenerId);

This example registers a listener that responds to any change to a change in the number of Row objects of a specific Table, and which also mutates the Store itself.

import {createStore} from 'tinybase';

const store = createStore().setTables({pets: {fido: {species: 'dog'}}});
const listenerId = store.addRowCountListener(
  'pets',
  (store, tableId, count) =>
    store.setCell('meta', 'update', tableId, count),
  true, // mutator
);

store.setRow('pets', 'felix', {species: 'cat'});
console.log(store.getTable('meta'));
// -> {update: {pets: 2}}

store.delListener(listenerId);

Since

v4.1.0