`useCreateQueries`

The useCreateQueries hook is used to create a Queries object within a React application with convenient memoization.

useCreateQueries(
  store: Store,
  create: (store: Store) => Queries,
  createDeps?: DependencyList,
): Queries

	Type	Description
`store`	`Store`	A reference to the `Store` for which to create a new `Queries` object.
`create`	`(store: Store) => Queries`	An optional callback for performing post-creation steps on the `Queries` object, such as adding definitions or listeners.
`createDeps?`	`DependencyList`	An optional array of dependencies for the `create` function, which, if any change, result in its rerun. This parameter defaults to an empty array.
returns	`Queries`	A reference to the `Queries` object.

It is possible to create a Queries object outside of the React app with the regular createQueries function and pass it in, but you may prefer to create it within the app, perhaps inside the top-level component. To defend against a new Queries object being created every time the app renders or re-renders, the useCreateQueries hook wraps the creation in a memoization.

The useCreateQueries hook is a very thin wrapper around the React useMemo hook, defaulting to the provided Store as its dependency, so that by default, the creation only occurs once per Store.

If your create function contains other dependencies, the changing of which should also cause the Queries object to be recreated, you can provide them in an array in the optional second parameter, just as you would for any React hook with dependencies.

This hook ensures the Queries object is destroyed whenever a new one is created or the component is unmounted.

Examples

This example creates a Queries object at the top level of a React application. Even though the App component is rendered twice, the Queries object creation only occurs once by default.

const App = () => {
  const store = useCreateStore(() =>
    createStore().setTable('pets', {
      fido: {species: 'dog', color: 'brown'},
      felix: {species: 'cat', color: 'black'},
      cujo: {species: 'dog', color: 'black'},
    }),
  );
  const queries = useCreateQueries(store, (store) => {
    console.log('Queries created');
    return createQueries(store).setQueryDefinition(
      'dogColors',
      'pets',
      ({select, where}) => {
        select('color');
        where('species', 'dog');
      },
    );
  });
  return (
    <span>{queries.getResultCell('dogColors', 'fido', 'color')}</span>
  );
};

const app = document.createElement('div');
const root = ReactDOMClient.createRoot(app);
root.render(<App />);
// -> 'Queries created'

root.render(<App />);
// No second Queries creation

console.log(app.innerHTML);
// -> '<span>brown</span>'

This example creates a Queries object at the top level of a React application. The App component is rendered twice, each with a different top-level prop. The useCreateQueries hook takes the resultCell prop as a dependency, and so the Queries object is created again on the second render.

const App = () => {
  const store = useCreateStore(() =>
    createStore().setTable('pets', {
      fido: {species: 'dog', color: 'brown'},
      felix: {species: 'cat', color: 'black'},
      cujo: {species: 'dog', color: 'black'},
    }),
  );
  const queries = useCreateQueries(store, (store) => {
    console.log('Queries created');
    return createQueries(store).setQueryDefinition(
      'dogColors',
      'pets',
      ({select, where}) => {
        select('color');
        where('species', 'dog');
      },
    );
  });
  return (
    <span>{queries.getResultCell('dogColors', 'fido', 'color')}</span>
  );
};

const app = document.createElement('div');
const root = ReactDOMClient.createRoot(app);
root.render(<App />);
// -> 'Queries created'

root.render(<App />);
// No second Queries creation

console.log(app.innerHTML);
// -> '<span>brown</span>'

Since

v2.0.0