useList

Hook function for efficient rendering of list store. Every item will be memoized and updated only when their data change.

useList(store, fn)

Formulae

useList<T>(
  store: Store<T[]>,
  fn: (value: T, index: number) => React.ReactNode
): React.ReactNode

Arguments

1. store (Store): Store with an array of items
2. fn (Function): Render function which will be called for every item in list

Returns

(React.Node

useList(store, config)

Formulae

useList<T>(
  store: Store<T[]>,
  config: {
    keys: any[]
    fn: (value: T, index: number) => React.ReactNode
    getKey?: (value: T) => React.Key
    placeholder?: React.ReactNode
  }
): React.ReactNode

Used when you need to pass dependencies to react (to update items when some of its dependencies are changed).

By default, useList rerenders only when some of its items were changed. However, sometimes we need to update items when some external value (e.g. props field or state of another store) changes. In such case, we need to tell React about our dependencies and pass keys explicitly.

Arguments

1. store (Store): Store with an array of items
2. keys (Array): Array of dependencies, which will be passed to react by useList
3. fn (Function): Render function which will be called for every item in list
4. getKey ((value) => React.Key): Optional function to compute key for every item of list
5. placeholder (ReactNode): Optional react node to render instead of an empty list

Examples

Example 1

import { createStore } from "effector";
import { useList } from "effector-react";

const $users = createStore([
  { id: 1, name: "Yung" },
  { id: 2, name: "Lean" },
  { id: 3, name: "Kyoto" },
  { id: 4, name: "Sesh" },
]);

const App = () => {
  // we don't need keys here any more
  const list = useList($users, ({ name }, index) => (
    <li>
      [{index}] {name}
    </li>
  ));

  return <ul>{list}</ul>;
};

Try it

Example 2

import { createStore, createEvent } from "effector";
import { useList } from "effector-react";

const addTodo = createEvent();
const toggleTodo = createEvent();

const $todoList = createStore([
  { text: "write useList example", done: true },
  { text: "update readme", done: false },
])
  .on(toggleTodo, (list, id) =>
    list.map((todo, i) => {
      if (i === id)
        return {
          ...todo,
          done: !todo.done,
        };
      return todo;
    }),
  )
  .on(addTodo, (list, e) => [
    ...list,
    {
      text: e.currentTarget.elements.content.value,
      done: false,
    },
  ]);

addTodo.watch((e) => {
  e.preventDefault();
});

const TodoList = () =>
  useList($todoList, ({ text, done }, i) => {
    const todo = done ? (
      <del>
        <span>{text}</span>
      </del>
    ) : (
      <span>{text}</span>
    );
    return <li onClick={() => toggleTodo(i)}>{todo}</li>;
  });
const App = () => (
  <div>
    <h1>todo list</h1>
    <form onSubmit={addTodo}>
      <label htmlFor="content">New todo</label>
      <input type="text" name="content" required />
      <input type="submit" value="Add" />
    </form>
    <ul>
      <TodoList />
    </ul>
  </div>
);

Try it

Example with config

import ReactDOM from "react-dom";
import { createEvent, createStore, restore } from "effector";
import { useStore, useList } from "effector-react";

const renameUser = createEvent();

const $user = restore(renameUser, "alice");
const $friends = createStore(["bob"]);

const App = () => {
  const user = useStore($user);

  return useList($friends, {
    keys: [user],
    fn: (friend) => (
      <div>
        {friend} is a friend of {user}
      </div>
    ),
  });
};

ReactDOM.render(<App />, document.getElementById("root"));
// => <div> bob is a friend of alice </div>

setTimeout(() => {
  renameUser("carol");
  // => <div> bob is a friend of carol </div>
}, 500);

Try it