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useResultRowCountListener

The useResultRowCountListener hook registers a listener function with a Queries object that will be called whenever the count of ResultRow objects in a ResultTable changes.

useResultRowCountListener(
  queryId: IdOrNull,
  listener: ResultRowCountListener,
  listenerDeps?: DependencyList,
  queriesOrQueriesId?: QueriesOrQueriesId,
): void
TypeDescription
queryIdIdOrNull

The Id of the query to listen to, or null as a wildcard.

listenerResultRowCountListener

The function that will be called whenever the Row Ids in the matching ResultTable change.

listenerDeps?DependencyList

An optional array of dependencies for the listener function, which, if any change, result in the re-registration of the listener. This parameter defaults to an empty array.

queriesOrQueriesId?QueriesOrQueriesId

The Queries object to register the listener with: omit for the default context Queries object, provide an Id for a named context Queries object, or provide an explicit reference.

returnsvoid

This has no return value.

This hook is useful for situations where a component needs to register its own specific listener to do more than simply tracking the value (which is more easily done with the useResultRowCount hook).

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

Unlike the addResultRowCountListener method, which returns a listener Id and requires you to remove it manually, the useResultRowCountListener hook manages this lifecycle for you: when the listener changes (per its listenerDeps dependencies) or the component unmounts, the listener on the underlying Queries object will be deleted.

Example

This example uses the useResultRowCountListener hook to create a listener that is scoped to a single component. When the component is unmounted, the listener is removed from the Queries object.

import {Provider, useResultRowCountListener} from 'tinybase/ui-react';
import {createQueries, createStore} from 'tinybase';
import React from 'react';
import {createRoot} from 'react-dom/client';

const App = ({queries}) => (
  <Provider queries={queries}>
    <Pane />
  </Provider>
);
const Pane = () => {
  useResultRowCountListener('petColors', () =>
    console.log('Result Row count changed'),
  );
  return <span>App</span>;
};

const store = createStore().setTable('pets', {
  fido: {species: 'dog', color: 'brown'},
  felix: {species: 'cat', color: 'black'},
  cujo: {species: 'dog', color: 'black'},
});
const queries = createQueries(store).setQueryDefinition(
  'petColors',
  'pets',
  ({select}) => select('color'),
);
const app = document.createElement('div');
const root = createRoot(app);
root.render(<App queries={queries} />);
console.log(queries.getListenerStats().rowCount);
// -> 1

store.setRow('pets', 'rex', {species: 'dog', color: 'tan'});
// -> 'Result Row count changed'

root.unmount();
console.log(queries.getListenerStats().rowCount);
// -> 0

Since

v4.1.0