Forms

Example 1

import React from "react";
import ReactDOM from "react-dom";
import { createEffect, createStore, createEvent, sample } from "effector";
import { useStoreMap } from "effector-react";

const formSubmitted = createEvent();
const fieldUpdate = createEvent();

const sendFormFx = createEffect((params) => {
  console.log(params);
});

const $form = createStore({});

$form.on(fieldUpdate, (form, { key, value }) => ({
  ...form,
  [key]: value,
}));

sample({
  clock: formSubmitted,
  source: $form,
  target: sendFormFx,
});

const handleChange = fieldUpdate.prepend((event) => ({
  key: event.target.name,
  value: event.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={formSubmitted}>
    <Field name="login" label="Login" />
    <Field name="password" type="password" label="Password" />
    <button type="submit">Submit!</button>
  </form>
);

formSubmitted.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 formSubmitted = createEvent(); // will be used further, and indicates, we have an intention to submit form
const fieldUpdate = createEvent(); //has intention to change $form's state in a way, defined in reducer further
const $form = createStore({});

$form.on(fieldUpdate, (form, { key, value }) => ({
  ...form,
  [key]: value,
}));

The next piece of code shows how we can obtain a state in effector in the 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({
  clock: formSubmitted, // when `formSubmitted` is triggered
  source: $form, // Take LATEST state from $form, and
  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 fieldUpdate event.

const handleChange = fieldUpdate.prepend((event) => ({
  key: event.target.name,
  value: event.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 the default html form submit behavior using react event from submitted:

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

Example 2

This example demonstrates how to manage state by using an uncontrolled form, handle data loading, create components that depend on stores, and transform data passed between events.

import React from "react";
import ReactDOM from "react-dom";
import { createEffect, createStore } from "effector";
import { useUnit, 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 = useUnit(sendFormFx.pending); //typeof loading === "boolean"

  return loading ? <div>Loading...</div> : null;
};

const SubmitButton = createComponent(sendFormFx.pending, (props, loading) => (
  //approach #2: implicit store usage
  //actually `createComponent` is deprecated
  <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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