solid-orange

TypeScript: pass result of useForm as component props

Hi, I am trying to pass my form created by useForm via props to a child component but I am not sure how to properly type it in the TypeScript. Here is an example:

import { ReactNode } from "react";
import { useForm } from "@tanstack/react-form";

function Parent() {
  const form = useForm({
    defaultValues: {
      emailAddress: "",
    },
    onSubmit: async ({ value }) => {
      alert(value.emailAddress);
    },
  });

  return (
    // following line shows type error
    <Child form={form}>
      {(form) => (
        <form.Field
          name="emailAddress"
          children={(field) => (
            // render the form field
            <></>
          )}
        />
      )}
    </Child>
  );
}

function Child<TForm extends ReturnType<typeof useForm>>(props: {
  readonly form: TForm;
  readonly children: (form: TForm) => ReactNode;
}) {
  return (
    <form
      onSubmit={(e) => {
        e.preventDefault();
        e.stopPropagation();
        props.form.handleSubmit();
      }}
    >
      {/* here goes some additional markup */}
      {props.children(props.form)}
      <props.form.Subscribe
        selector={(state) => [state.canSubmit, state.isSubmitting]}
        children={([canSubmit]) => (
          <Button variant="contained" type="submit" disabled={!canSubmit}>
            Submit
          </Button>
        )}
      />
    </form>
  );
}

import { ReactNode } from "react";
import { useForm } from "@tanstack/react-form";

function Parent() {
  const form = useForm({
    defaultValues: {
      emailAddress: "",
    },
    onSubmit: async ({ value }) => {
      alert(value.emailAddress);
    },
  });

  return (
    // following line shows type error
    <Child form={form}>
      {(form) => (
        <form.Field
          name="emailAddress"
          children={(field) => (
            // render the form field
            <></>
          )}
        />
      )}
    </Child>
  );
}

function Child<TForm extends ReturnType<typeof useForm>>(props: {
  readonly form: TForm;
  readonly children: (form: TForm) => ReactNode;
}) {
  return (
    <form
      onSubmit={(e) => {
        e.preventDefault();
        e.stopPropagation();
        props.form.handleSubmit();
      }}
    >
      {/* here goes some additional markup */}
      {props.children(props.form)}
      <props.form.Subscribe
        selector={(state) => [state.canSubmit, state.isSubmitting]}
        children={([canSubmit]) => (
          <Button variant="contained" type="submit" disabled={!canSubmit}>
            Submit
          </Button>
        )}
      />
    </form>
  );
}

Type error shown:

Type 'ReactFormExtendedApi<{ emailAddress: string; }, FormValidateOrFn<{ emailAddress: string; }> | undefined, FormValidateOrFn<{ emailAddress: string; }> | undefined, ... 6 more ..., unknown>' is not assignable to type 'ReactFormExtendedApi<unknown, FormValidateOrFn<unknown> | undefined, FormValidateOrFn<unknown> | undefined, FormAsyncValidateOrFn<unknown> | undefined, ... 5 more ..., unknown>'.

10 Replies

solid-orangeOP•3mo ago

I understand that the problem is with Child type notation:

import { useForm } from "@tanstack/react-form";

function Child<TForm extends ReturnType<typeof useForm>>() {}

import { useForm } from "@tanstack/react-form";

function Child<TForm extends ReturnType<typeof useForm>>() {}

It should probably be something like this:

import { ReactFormExtendedApi } from "@tanstack/react-form";

function Child<TForm extends ReactFormExtendedApi>() {}

import { ReactFormExtendedApi } from "@tanstack/react-form";

function Child<TForm extends ReactFormExtendedApi>() {}

Unfortunately ReactFormExtendedApi type expects 10 type arguments.

Generic type 'ReactFormExtendedApi' requires 10 type argument(s). (ts 2314)

Has anyone tried this already? Is there a better/easier way? Or do I need to fill in all the 10 type arguments?

genetic-orange•3mo ago

withForm allows you to safely type the form prop and you won‘t need to type the generics yourself

solid-orangeOP•3mo ago

Can you provide an example, please? Or point me to the documentation?

genetic-orange•3mo ago

Sure, one sec

genetic-orange•3mo ago

https://tanstack.com/form/latest/docs/framework/react/guides/form-composition

Form Composition | TanStack Form React Docs

A common criticism of TanStack Form is its verbosity out-of-the-box. While this can be useful for educational purposes helping enforce understanding our APIs it's not ideal in production use cases. As...

solid-orangeOP•3mo ago

Thanks for the link. I have read the documentation but I think that this time this is not something which can help me. I am trying to pass form into child component and I need kind of generic way of doing this as for instance my submit button is not rendered in parent component but I want it to be "hidden" as an implementation detail in my child component. I ended up with custom type as I didn't really need to do anything with the data - I only needed handleSubmit and Subscribe, this is what I ended up with:

import { ReactNode } from "react";

function Child(props: {
    readonly form: {
      handleSubmit: () => Promise<void>;
      Subscribe: (props: {
        selector: (state: {
          canSubmit: boolean;
          isSubmitting: boolean;
        }) => [boolean, boolean];
        children: (props: [boolean, boolean]) => ReactNode;
      }) => ReactNode;
    };
}) {
  /* component here */
}

import { ReactNode } from "react";

function Child(props: {
    readonly form: {
      handleSubmit: () => Promise<void>;
      Subscribe: (props: {
        selector: (state: {
          canSubmit: boolean;
          isSubmitting: boolean;
        }) => [boolean, boolean];
        children: (props: [boolean, boolean]) => ReactNode;
      }) => ReactNode;
    };
}) {
  /* component here */
}

Thanks anyway!

genetic-orange•3mo ago

oh, this sounds like a classic example of a form component same docs section, where you can just use any form through context in that case, accessing its non-values state

solid-orangeOP•3mo ago

Thank you for your reply! I am not sure if I can imagine what you suggest. Would you be able to give me some code example? (does not to be proper code, just pseudo code). This is not urgent as I already have a workaround. If you would find few minutes of your time that would be great. I am using MUI 7 Dialog component (https://mui.com/material-ui/react-dialog/) Basically my structure looks like this:

function CustomDialog(props: {form}) {
  return (
    <Dialog>
      <DialogTitle />
      <form onSubmit={() => props.form.handleSubmit()}>
        <DialogContent>{children}</DialogContent>
        <DialogActions>
          <Button>Cancel</Button>
          <props.form.Subscribe />
        </DialogActions>
      </form>
    </Dialog>
  )
}

function CustomDialog(props: {form}) {
  return (
    <Dialog>
      <DialogTitle />
      <form onSubmit={() => props.form.handleSubmit()}>
        <DialogContent>{children}</DialogContent>
        <DialogActions>
          <Button>Cancel</Button>
          <props.form.Subscribe />
        </DialogActions>
      </form>
    </Dialog>
  )
}

The <form /> uses handleSubmit() from props.form and <DialogActions /> contains Subscribe for rendering submit button from props.form as well. Correct me if I am mistaken since I am not sure how exactly this works, but wouldn't I need custom hook for each form I would like to render within my <CustomDialog /> component?

React Dialog component - Material UI

Dialogs inform users about a task and can contain critical information, require decisions, or involve multiple tasks.

solid-orangeOP•3mo ago

In the meantime I am going to RTFM - I have a feeling that just quickly skimming through few sections is not sufficient. I am sorry for wasting your time as I believe that everything is already written down in the documentation.

genetic-orange•3mo ago

with form composition, you can use useFormContext and get a general form API to work with. This doesn't include the form's values (as any form could use them), but it includes most meta state and sections you need.

// your-hook.tsx
export const { useFormContext, useFieldContext, formContext, fieldContext } = createFormHookContexts();

// submit-button.tsx
function SubmitButton(props: ButtonProps) {
  const form = useFormContext();

  // you can now use form.Subscribe, form state etc.
  // render the button that you need
  return <form.Subscribe selector={state => state.canSubmit}>
    {canSubmit => <button {...props} disabled={props.disabled || !canSubmit}>Submit</button>}
  </form.Subscribe>
}

// when creating your hook
const { useAppForm } = createFormHook({
   fieldContext, formContext,
   fieldComponents: {},
   formComponents: { SubmitButton }
})

// Usage
const form = useAppForm({
   // ... what you'd do for useForm
})

// Create context
return <form.AppForm>
  <form.SubmitButton />
</form.AppForm>

// your-hook.tsx
export const { useFormContext, useFieldContext, formContext, fieldContext } = createFormHookContexts();

// submit-button.tsx
function SubmitButton(props: ButtonProps) {
  const form = useFormContext();

  // you can now use form.Subscribe, form state etc.
  // render the button that you need
  return <form.Subscribe selector={state => state.canSubmit}>
    {canSubmit => <button {...props} disabled={props.disabled || !canSubmit}>Submit</button>}
  </form.Subscribe>
}

// when creating your hook
const { useAppForm } = createFormHook({
   fieldContext, formContext,
   fieldComponents: {},
   formComponents: { SubmitButton }
})

// Usage
const form = useAppForm({
   // ... what you'd do for useForm
})

// Create context
return <form.AppForm>
  <form.SubmitButton />
</form.AppForm>

since it's context, you can also nest them so you can have a form SubmitButton inside a form Dialog wrapper without problem what usually confuses people is that this context is stable, so make sure to use reactive state access like form.Subscribe

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TypeScript: pass result of useForm as component props

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