Unform

Unform is an open-source library for building forms in React and React Native. It was created by Rocketseat and provides a lightweight, reusable approach to form management that emphasizes performance and simplicity. The library centers on using a single form reference and uncontrolled inputs to minimize re-renders, which can be advantageous in large or complex forms.

Design and core ideas: Unform collects form data when the form is submitted, rather than storing every field value in React state. Fields register with the form using a field name, and custom input components connect to the form through this registration mechanism. The Form component serves as a container and accepts an onSubmit handler, along with optional initial data and other configuration. The form reference enables programmatic actions such as setting values, resetting the form, or applying validation errors.

Validation and error handling: Unform does not enforce a particular validation strategy, allowing developers to integrate their preferred validators (for example, Yup or custom logic). Validation can be executed before submission, and errors can be surfaced to fields through the form reference, enabling consistent error display without requiring per-field re-renders.

Usage and ecosystem: Typical usage involves wrapping inputs in a Form, providing an onSubmit function, and rendering custom input components that connect to the form via their field names. Unform supports both web and React Native environments, and can be extended with custom input components to fit various use cases. It sits alongside other form libraries as an option for developers prioritizing performance and a minimal, imperative style of form management.