useStoreMap

Function, which subscribes to a store and transforms its value with a given function. Signal will update only when the selector function result will change

useStoreMap(store, fn)

Common use case: subscribe to changes in selected part of store only

useStoreMap<State, Result>(
  store: Store<State>,
  fn: (state: State) => Result
): Accessor<Result>

Arguments

  1. store: Source store
  2. fn ((state) => result): Selector function to receive part of source store

Returns

(Result)

useStoreMap(config)

useStoreMap({ store, keys, fn, updateFilter });

Arguments

  1. params (Object): Configuration object
    • store: Source store
    • keys (Array): Will be passed to fn selector
    • fn ((state, keys) => result): Selector function to receive part of source store
    • updateFilter ((newResult, oldResult) => boolean): Optional function used to compare old and new updates to prevent unnecessary rerenders. Uses createStore updateFilter option under the hood

Returns

(Accessor<Result>)

Example

This hook is very useful for working with lists, especially with large ones

import { createStore } from "effector";
import { useUnit, useStoreMap } from "effector-solid";
import { For } from "solid-js/web";

const data = [
  {
    id: 1,
    name: "Yung",
  },
  {
    id: 2,
    name: "Lean",
  },
  {
    id: 3,
    name: "Kyoto",
  },
  {
    id: 4,
    name: "Sesh",
  },
];

const $users = createStore(data);
const $ids = createStore(data.map(({ id }) => id));

const User = ({ id }) => {
  const user = useStoreMap({
    store: $users,
    keys: [id],
    fn: (users, [userId]) => users.find(({ id }) => id === userId),
  });

  return (
    <div>
      <strong>[{user().id}]</strong> {user().name}
    </div>
  );
};

const UserList = () => {
  const ids = useUnit($ids);

  return <For each={ids()}>{(id) => <User key={id} id={id} />}</For>;
};
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