`useLocalRowIdsListener`

The useLocalRowIdsListener hook registers a listener function with the Relationships object that will be called whenever the local Row Ids in a Relationship change.

useLocalRowIdsListener(
  relationshipId: IdOrNull,
  remoteRowId: IdOrNull,
  listener: LocalRowIdsListener,
  listenerDeps?: DependencyList,
  relationshipsOrRelationshipsId?: any,
): void

	Type	Description
`relationshipId`	`IdOrNull`	The `Id` of the `Relationship` to listen to, or `null` as a wildcard.
`remoteRowId`	`IdOrNull`	The `Id` of the remote `Row` to listen to, or `null` as a wildcard.
`listener`	`LocalRowIdsListener`	The function that will be called whenever the local `Row` `Ids` 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.
`relationshipsOrRelationshipsId?`	`any`	The `Relationships` object to register the listener with: omit for the default context `Relationships` object, provide an `Id` for a named context `Relationships` 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 useLocalRowsId hook).

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

Both, either, or neither of the relationshipId and remoteRowId parameters can be wildcarded with null. You can listen to a specific remote Row in a specific Relationship, any remote Row in a specific Relationship, a specific remote Row in any Relationship, or any remote Row in any Relationship.

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

Example

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

const App = ({relationships}) => (
  <Provider relationships={relationships}>
    <Pane />
  </Provider>
);
const Pane = () => {
  useLocalRowIdsListener('petSpecies', 'dog', () =>
    console.log('Local Row Ids changed'),
  );
  return <span>App</span>;
};

const store = createStore()
  .setTable('pets', {fido: {species: 'dog'}, cujo: {species: 'dog'}})
  .setTable('species', {wolf: {price: 10}, dog: {price: 5}});
const relationships = createRelationships(store);
relationships.setRelationshipDefinition(
  'petSpecies',
  'pets',
  'species',
  'species',
);

const app = document.createElement('div');
const root = ReactDOMClient.createRoot(app);
root.render(<App relationships={relationships} />);
console.log(relationships.getListenerStats().localRowIds);
// -> 1

store.setRow('pets', 'toto', {species: 'dog'});
// -> 'Local Row Ids changed'

root.unmount();
console.log(relationships.getListenerStats().localRowIds);
// -> 0