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({handler: console.log})
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 action="javascript:void(0)" onSubmit={submitted}>
    <Field name="login" label="Login" />
    <Field name="password" type="password" label="Password" />
    <button type="submit">Submit!</button>
  </form>
)

ReactDOM.render(<App />, document.getElementById('root'))

Try it

Let's break down the code above.

These are just events & effects definitions. Simple.

const sendFormFx = createEffect({handler: console.log})
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
    action="void(0)"
    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>
)

Of course, there is much simplier way, to implement this, consider:

const sendFormFx = createEffect({handler: () => console.log($store.getState())})
const changed = createEvent()
const $store = createStore({}).on(changed, (s, e) => ({
  ...s,
  [e.target.name]: e.target.value,
}))

const App = () => {
  const values = useStore($store)

  return (
    <form
      action="void(0)"
      onSubmit={sendFormFx /*note, there is an effect itself*/}>
      <input
        name="login"
        label="Login"
        onChange={changed}
        value={values.login || ''}
      />
      <input
        name="password"
        type="password"
        label="Password"
        onChange={changed}
        value={values.password || ''}
      />
      <button type="submit">Submit!</button>
    </form>
  )
}

ReactDOM.render(<App />, document.getElementById('root'))

Try it

This code is way shorter, yet has code duplication, lower scalability and less reusable. In some cases, usage of getState may cause state inconsistence, race conditions.

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'

const sendFormFx = createEffect({
  //defining simple Effect, which results a string in 3 seconds
  handler: formData =>
    new Promise(rs =>
      setTimeout(rs, 3000, `Signed in as [${formData.get('name')}]`),
    ),
})

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, hooks are unsupported yet
  <button disabled={loading} type="submit">
    Submit
  </button>
))

const onSubmit = sendFormFx.prepend(e => new FormData(e.target)) //transforming upcoming data, from DOM Event to FormData

const App = () => {
  React.useEffect(() => sendFormFx.done.watch(({result}) => alert(result)), []) //applying side-effect, upon sendFormFx `done`

  return (
    <form action="javascript:void(0)" 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