Forms

Example 1

import React from 'react'
import ReactDOM from 'react-dom'
import {createEffect, createStore, createEvent, sample} from 'effector'
import {useStore, useStoreMap} from 'effector-react'
const sendFormFx = createEffect(params => {
console.log(params)
})
const submitted = createEvent()
const setField = createEvent()
const $form = createStore({}).on(setField, (s, {key, value}) => ({
...s,
[key]: value,
}))
sample({
source: $form,
clock: submitted,
target: sendFormFx,
})
const handleChange = setField.prepend(e => ({
key: e.target.name,
value: e.target.value,
}))
const Field = ({name, type, label}) => {
const value = useStoreMap({
store: $form,
keys: [name],
fn: values => values[name] || '',
})
return (
<div>
{label}{' '}
<input name={name} type={type} value={value} onChange={handleChange} />
</div>
)
}
const App = () => (
<form onSubmit={submitted}>
<Field name="login" label="Login" />
<Field name="password" type="password" label="Password" />
<button type="submit">Submit!</button>
</form>
)
submitted.watch(e => {
e.preventDefault()
})
ReactDOM.render(<App />, document.getElementById('root'))

Try it

Let's break down the code above.

These are just events & effects definitions.

const sendFormFx = createEffect(params => {
console.log(params)
})
const submitted = createEvent() // will be used further, and indicates, we have an intention to submit form
const setField = createEvent() //has intention to change $form's state in a way, defined in reducer further
const $form = createStore({}).on(setField, (s, {key, value}) => ({
...s,
[key]: value,
}))

Next piece of code shows how we can obtain a state in effector in a right way. This kind of state retrieving provides state consistency, and removes any possible race conditions, which can occur in some cases, when using getState.

sample({
source: $form, // Take LATEST state from $form, and
clock: submitted, // when `submitted` is triggered
target: sendFormFx, // pass it to `sendFormFx`, in other words -> sendFormFx(state)
//fn: (sourceState, clockParams) => transformedData // we could additionally transform data here, but if we need just pass source's value, we may omit this property
})

So far, so good, we've almost set up our model (events, effects and stores). Next thing is to create event, which will be used as onChange callback, which requires some data transformation, before data appear in setField event.

const handleChange = setField.prepend(e => ({
key: e.target.name,
value: e.target.value,
})) // upon trigger `handleChange`, passed data will be transformed in a way, described in function above, and returning value will be passed to original `setField` event.

Next, we have to deal with how inputs should work. useStoreMap hook here prevents component rerender upon non-relevant changes.

const Field = ({name, type, label}) => {
const value = useStoreMap({
store: $form, // take $form's state
keys: [name], // watch for changes of `name`
fn: values => values[name] || '', // retrieve data from $form's state in this way (note: there will be an error, if undefined is returned)
})
return (
<div>
{label}{' '}
<input
name={name}
type={type}
value={value}
onChange={handleChange /*note, bound event is here!*/}
/>
</div>
)
}

And, finally, the App itself! Note, how we got rid of any business-logic in view layer. It's simpler to debug, to share logic, and even more: logic is framework independent now.

const App = () => (
<form
onSubmit={submitted /*note, there is an event, which is clock for sample*/}>
<Field name="login" label="Login" />
<Field name="password" type="password" label="Password" />
<button type="submit">Submit!</button>
</form>
)

Prevent default html form submit behavior using react event from submitted

submitted.watch(e => {
e.preventDefault()
})

Example 2

This example shows, how you can manage state with uncontrolled form, handling loading of data, create components which dependend on stores, transform data passed between events.

import React from 'react'
import ReactDOM from 'react-dom'
import {createEffect, createStore} from 'effector'
import {useStore, createComponent} from 'effector-react'
//defining simple Effect, which results a string in 3 seconds
const sendFormFx = createEffect(
formData =>
new Promise(rs =>
setTimeout(rs, 1000, `Signed in as [${formData.get('name')}]`),
),
)
//applying side-effect, upon sendFormFx `doneData`
sendFormFx.doneData.watch(result => {
console.log(result)
})
const Loader = () => {
//approach #1: explicit store usage, with hook `useStore`
const loading = useStore(sendFormFx.pending) //typeof loading === "boolean"
return loading ? <div>Loading...</div> : null
}
const SubmitButton = createComponent(sendFormFx.pending, (props, loading) => (
//approach #2: implicit store usage
<button disabled={loading} type="submit">
Submit
</button>
))
const onSubmit = sendFormFx.prepend(e => new FormData(e.target)) //transforming upcoming data, from DOM Event to FormData
onSubmit.watch(e => {
e.preventDefault()
})
const App = () => (
<form onSubmit={onSubmit}>
Login: <input name="name" />
<br />
Password: <input name="password" type="password" />
<br />
<Loader />
<SubmitButton />
</form>
)
ReactDOM.render(<App />, document.getElementById('root'))

Try it

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