`useParamValuesListener`

The useParamValuesListener hook registers a listener function with a Queries object that will be called whenever the parameter values for a query change.

useParamValuesListener(
  queryId: IdOrNull,
  listener: ParamValuesListener,
  listenerDeps?: DependencyList,
  queriesOrQueriesId?: QueriesOrQueriesId,
): void

	Type	Description
`queryId`	`IdOrNull`	The `Id` of the query to listen to, or `null` as a wildcard.
`listener`	`ParamValuesListener`	The function that will be called whenever the parameter values for the query 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.
returns	`void`	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 values (which is more easily done with the useParamValues hook).

Unlike the addParamValuesListener method, which returns a listener Id and requires you to remove it manually, the useParamValuesListener 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 useParamValuesListener 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 React from 'react';
import {createRoot} from 'react-dom/client';
import {createQueries, createStore} from 'tinybase';
import {Provider, useParamValuesListener} from 'tinybase/ui-react';

const App = ({queries}) => (
  <Provider queries={queries}>
    <Pane />
  </Provider>
);
const Pane = () => {
  useParamValuesListener('petsBySpecies', () =>
    console.log('Param values changed'),
  );
  return <span>App</span>;
};

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

queries.setParamValue('petsBySpecies', 'species', 'cat');
// -> 'Param values changed'

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

Since

v7.2.0