createEffect

[ ru ]

Method for creating an effect

createEffect with handler

Creates an effect with given handler

createEffect(handler?)

Arguments

  1. handler (Function): function to handle effect calls, also can be set with use(handler)

Returns

Effect: New effect

Reminder

You must provide a handler either in createEffect or in .use method later, otherwise effect will throw with no handler used in _%effect name%_ error.

Examples

Create effect with handler

import { createEffect } from "effector";

const fetchUserReposFx = createEffect(async ({ name }) => {
  const url = `https://api.github.com/users/${name}/repos`;
  const req = await fetch(url);
  return req.json();
});

fetchUserReposFx.done.watch(({ params, result }) => {
  console.log(result);
});

await fetchUserReposFx({ name: "zerobias" });

Try it

Change state on effect completion

import { createStore, createEffect } from "effector";

const fetchUserReposFx = createEffect(async ({ name }) => {
  const url = `https://api.github.com/users/${name}/repos`;
  const req = await fetch(url);
  return req.json();
});

const $repos = createStore([]).on(fetchUserReposFx.doneData, (_, repos) => repos);

$repos.watch((repos) => {
  console.log(`${repos.length} repos`);
});
// => 0 repos

await fetchUserReposFx({ name: "zerobias" });
// => 26 repos

Try it

Set handler to effect after creating

import { createEffect } from "effector";

const fetchUserReposFx = createEffect();

fetchUserReposFx.use(async ({ name }) => {
  const url = `https://api.github.com/users/${name}/repos`;
  const req = await fetch(url);
  return req.json();
});

await fetchUserReposFx({ name: "zerobias" });

Try it

Watch effect status

import { createEffect } from "effector";

const fetchUserReposFx = createEffect(async ({ name }) => {
  const url = `https://api.github.com/users/${name}/repos`;
  const req = await fetch(url);
  return req.json();
});

fetchUserReposFx.pending.watch((pending) => {
  console.log(`effect is pending?: ${pending ? "yes" : "no"}`);
});

fetchUserReposFx.done.watch(({ params, result }) => {
  console.log(params); // {name: 'zerobias'}
  console.log(result); // resolved value
});

fetchUserReposFx.fail.watch(({ params, error }) => {
  console.error(params); // {name: 'zerobias'}
  console.error(error); // rejected value
});

fetchUserReposFx.finally.watch(({ params, status, result, error }) => {
  console.log(params); // {name: 'zerobias'}
  console.log(`handler status: ${status}`);

  if (error) {
    console.log("handler rejected", error);
  } else {
    console.log("handler resolved", result);
  }
});

await fetchUserReposFx({ name: "zerobias" });

Try it

createEffect with config

Creates an effect with handler and name from a given config object

createEffect({ handler, name });

Arguments

  1. config? (Params): effect
    • handler (Function): function to handle effect calls, also can be set with use(handler)
    • name? (string): Optional effect name

Returns

Effect: New effect

Examples

Create named effect

import { createEffect } from "effector";

const fetchUserReposFx = createEffect({
  name: "fetch user repositories",
  async handler({ name }) {
    const url = `https://api.github.com/users/${name}/repos`;
    const req = await fetch(url);
    return req.json();
  },
});

await fetchUserReposFx({ name: "zerobias" });

Try it

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