`useParamValueListener`

The useParamValueListener hook registers a listener function with a Queries object that will be called whenever a single parameter value for a query changes.

useParamValueListener(
  queryId: IdOrNull,
  paramId: IdOrNull,
  listener: ParamValueListener,
  listenerDeps?: DependencyList,
  queriesOrQueriesId?: QueriesOrQueriesId,
): void

	Type	Description
`queryId`	`IdOrNull`	The `Id` of the query to listen to, or `null` as a wildcard.
`paramId`	`IdOrNull`	The `Id` of the parameter to listen to, or `null` as a wildcard.
`listener`	`ParamValueListener`	The function that will be called whenever the parameter value changes.
`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 value (which is more easily done with the useParamValue hook).

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

Both the queryId and paramId parameters can be wildcarded with null. You can listen to a specific parameter in a specific query, any parameter in any query, for example - or every other combination of wildcards.

Unlike the addParamValueListener method, which returns a listener Id and requires you to remove it manually, the useParamValueListener 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 useParamValueListener 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, useParamValueListener} from 'tinybase/ui-react';

const App = ({queries}) => (
  <Provider queries={queries}>
    <Pane />
  </Provider>
);
const Pane = () => {
  useParamValueListener('petsBySpecies', 'species', () =>
    console.log('Param value 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().paramValue);
// -> 1

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

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

Since

v7.2.0