UI ライブラリとのインテグレーション

In this guide, we'll walk through how to integrate Conform with custom input components.

#Concept

Conform supports native inputs out of the box by listening for form events like input, focusout, and reset on the document. This means simple custom components that wrap native elements (e.g. a styled <input>) typically work without extra setup.

However, more complex inputs like <Select />, <DatePicker />, or custom file uploaders often involve additional layers of abstraction. These layers interfere with how the browser emits native form events, making it harder for Conform to track user interactions.

To solve this, we provide the useControl hook. It lets you manually connect a hidden base input to a custom UI component and dispatch native events in response to user interaction.

#Emulating Native Inputs

There are multiple ways to wire up a base input with useControl:

In some cases, you may be able to re-use an input rendered by the UI library. This can help with progressive enhancement — for instance, when a user clicks on a styled label that toggles a real hidden checkbox using standard HTML behavior. The form still submits correctly even if JavaScript hasn't loaded.
But not all custom inputs enable this. Some UI libraries render hidden inputs and update their value via JavaScript after interacting with entirely separate elements. These setups won't work before JavaScript loads and may trigger their event handler in an unexpected order — for example, calling onChange before updating the input's value.
Because useControl itself requires JavaScript, the benefits of re-using library-provided inputs are marginal. We recommend rendering your own base input unless you're confident it helps with progressive enhancement and behaves as expected.

The useControl hook gives you a control object that manages the input value and provides methods to trigger form events. Here are the main steps to integrate it:

Register a base input
- Render a hidden native input element (e.g. <input hidden />) and register it with control.register().
- This serves as the authoritative source of the value and emits native form events.
Emit form events
- Use control.change() and control.blur() in your custom component's onChange and onBlur handlers.
Make it controlled
- Use control.value, control.options, control.checked, or control.files to sync the custom component with the current state.
Delegate focus (optional)
- If your base input is hidden, use the onFocus callback in useControl to forward focus to the custom input for accessibility.

Example

1import { useControl } from '@conform-to/react/future';
2import { useForm } from '@conform-to/react';
3import { Input } from 'custom-ui-library';
4
5function MyInput({ name, defaultValue }) {
6  const control = useControl({ defaultValue });
7
8  return (
9    <>
10      <input name={name} ref={control.register} hidden />
11      <Input
12        value={control.value}
13        onChange={(value) => control.change(value)}
14        onBlur={() => control.blur()}
15      />
16    </>
17  );
18}

Input Type Differences

Input types contribute to form data in different ways when it comes to form submission. Here's a quick reference:

Text Inputs: Straightforward. When empty, the value is an empty string.
Checkboxes / Radios:
- Default value is 'on' unless value is specified.
- If checked, the value is submitted; if unchecked, it's omitted.
Select (single): Value is the selected option's value. Defaults to the first option.
Select (multiple): Represents an array of selected values. If none selected, no entry in FormData.
File Inputs: Yields one or more File objects. If empty, FormData omits the field.
Other inputs: Behave like text inputs. Their type adds context but doesn't affect how data is submitted.

#Examples

We've prepared examples for integrating with popular UI libraries:

If the library you're using isn't listed or you run into issues, open a discussion — we're happy to help. Contributions are also welcome if you'd like to share an example.