Count

What it is

useLensCount asks the graph how many entities a schema has. It calls lens.count() with no criteria. Use it for a total, and a rule for a derived value, as Schemas and LDKit describes.

Import

import { useLensCount, useSparqlOptions } from "@manta-eu/react/ldo-ui";

useSparqlOptions() takes no arguments and returns the LDKit Options for the connection set up by SparqlOptionsProvider.

Example

import { useLensCount, useSparqlOptions } from "@manta-eu/react/ldo-ui";
import { YourSchema } from "./.ldkit/your-namespace";

export function YourTotal() {
  const options = useSparqlOptions();
  const { data } = useLensCount({ schema: YourSchema, options, queryKey: ["your-entities", "count"] });

  return <p>{data ?? "…"}</p>;
}

Request

useLensCount({
  schema, // S
  options, // Options from useSparqlOptions()
  queryKey, // readonly unknown[]
  enabled, // boolean, optional, defaults to true
});

The parameter type is UseSparqlQueryOptions<S> with iri omitted. The hook passes no where and no max to lens.count(), so the number is every entity of the schema.

Response

The hook returns TanStack Query’s UseQueryResult<number, Error>.

{
  data: number | undefined;
  error: Error | null;
  status: "pending" | "error" | "success";
  isPending: boolean;
  isError: boolean;
  isSuccess: boolean;
}

data is the count once the query succeeds. lens.count() resolves to that number.