`useMetricListener`

The useMetricListener primitive registers a listener function with the Metrics object that will be called whenever the value of a specified Metric changes.

useMetricListener(
  metricId: MaybeAccessor<IdOrNull>,
  listener: MetricListener,
  metricsOrMetricsId?: MaybeAccessor<undefined | MetricsOrMetricsId>,
): void

	Type	Description
`metricId`	`MaybeAccessor<IdOrNull>`	The `Id` of the `Metric` to listen to, or `null` as a wildcard.
`listener`	`MetricListener`	The function that will be called whenever the `Metric` changes.
`metricsOrMetricsId?`	`MaybeAccessor<undefined \| MetricsOrMetricsId>`	The `Metrics` object to register the listener with: omit for the default context `Metrics` object, provide an `Id` for a named context `Metrics` object, or provide an explicit reference.
returns	`void`	This has no return value.

This primitive 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 useMetric primitive).

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

Unlike the addMetricListener method, which returns a listener Id and requires you to remove it manually, the useMetricListener primitive manages this lifecycle for you: when the component unmounts, the listener on the underlying Metrics object, will be deleted.

Example

This example creates the TinyBase objects needed by the Solid primitive or component and calls it from within a reactive root.

import {createRoot} from 'solid-js';
import {
  createCheckpoints,
  createIndexes,
  createMetrics,
  createQueries,
  createRelationships,
  createStore,
} from 'tinybase';
import {useMetricListener} from 'tinybase/ui-solid';

createRoot((dispose) => {
  const store = createStore()
    .setTables({
      pets: {
        fido: {species: 'dog', color: 'brown', next: 'felix'},
        felix: {species: 'cat', color: 'black'},
      },
      species: {dog: {price: 5}, cat: {price: 4}},
    })
    .setValues({open: true});
  const metrics = createMetrics(store).setMetricDefinition(
    'highestPrice',
    'species',
    'max',
    'price',
  );
  const indexes = createIndexes(store).setIndexDefinition(
    'bySpecies',
    'pets',
    'species',
  );
  const relationships = createRelationships(store)
    .setRelationshipDefinition('petSpecies', 'pets', 'species', 'species')
    .setRelationshipDefinition('nextPet', 'pets', 'pets', 'next');
  const queries = createQueries(store).setQueryDefinition(
    'petColors',
    'pets',
    ({select, where, param}) => {
      select('color');
      where((getCell) => getCell('species') == param('species'));
    },
    {species: 'dog'},
  );
  const checkpoints = createCheckpoints(store);
  store.setCell('pets', 'fido', 'color', 'walnut');
  checkpoints.setCheckpoint('updated color');
  metrics.getMetric('highestPrice');
  indexes.getSliceIds('bySpecies');
  relationships.getRemoteRowId('petSpecies', 'fido');
  queries.getResultRowIds('petColors');
  useMetricListener('highestPrice', () => undefined, metrics);
  dispose();
});

Since

v8.3.0