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Protocol @@unitShape


effector-react 22.4.0, effector-solid 0.22.7

Effector provides a way to use units (Stores, Events, Effects) in UI libraries with a special bindings like effector-react, effector-solid, etc. Normally, they allow to bind any shape of units to a UI-framework:

import {createStore} from 'effector'
import {useUnit} from 'effector-react'

const $value = createStore('Hello!')

const Component = () => {
const {value} = useUnit({value: $value})

return <p>{value}</p>

But what if you want to create your own library on top of Effector with some custom entities? For example, you want to create a router library with a custom Route entity, and you want to allow users to use it with effector-react bindings:

import {createRoute} from 'my-router-library'
import {useUnit} from 'effector-react'

const mainPageRoute = createRoute(/* ... */)

const Component = () => {
const {params} = useUnit(mainPageRoute)

return <p>{params.name}</p>

It is possible with the @@unitShape protocol. It allows to define a shape of a unit in your custom entity, and then use it in UI libraries. Just add field @@unitShape with a function that return shape of units to your entity:

function createRoute(/* ... */) {
const $params = createStore(/* ... */)

return {
'@@unitShape': () => ({
params: $params,


Q: How frequently @@unitShape-function is called?

A: As many times as useUnit itself is called - it depends on a UI-library. For example, effector-react calls it as any other hook - once per component render, but effector-solid calls useUnit once per component mount.

Q: How can I know what UI-library is used for particular @@unitShape call?

A: You cannot. @@unitShape has to be universal for all UI-libraries either has to check what UI-library is used inside by UI-library methods (like Context in React or Solid).