[React 19] Without extra Generic Type to useActionState hook

[PedroGuilhermeFariaDuarte]

Summary

Hi everyone!

I have a question about the types from the new hook 'useActionState'.

Actually, I'm working on a project and I need some extra types for my action function

Why don't we have an extra Generic Type to return from the action? Does the return really need to be equal to the initial state?

In a real use case, the return from the action can be different from the entry data, such as an error object like:

// INPUT DATA
{
  email: '[email protected]'  
}

// OUTPUT DATA
{
  email: {
    value: '[email protected]'  
    state: {
      error: {
         message: null
      }
    }
  }
}

Reference

• https://react.dev/reference/react/useActionState
• https://react.dev/blog/2024/12/05/react-19#whats-new-in-react-19

[eps1lon]

You can specify the full type by explicitly setting the type parameter. In your case that would be useActionState<{ email: string | {value: string, state: {error: {message: null}}}}>()