React Native, TypeScript, Formik: handleSubmit typings in onPress

Programming
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1

I’m trying to build a form in my React Native application with Typescript using Formik, following the tutorial guide and the Formik with RN section in JS.

When I tried to translate the example into typescript, I got the following typing error on the Button's onPress attribute:

No overload matches this call.
  Overload 1 of 2, '(props: Readonly<ButtonProps>): Button', gave the following error.
    Type '(e?: FormEvent<HTMLFormElement>) => void' is not assignable to type '(ev: NativeSyntheticEvent<NativeTouchEvent>) => void'.
      Types of parameters 'e' and 'ev' are incompatible.
        Type 'NativeSyntheticEvent<NativeTouchEvent>' is not assignable to type 'FormEvent<HTMLFormElement>'.
          Types of property 'nativeEvent' are incompatible.
            Type 'NativeTouchEvent' is missing the following properties from type 'Event': bubbles, cancelBubble, cancelable, composed, and 17 more.
  Overload 2 of 2, '(props: ButtonProps, context?: any): Button', gave the following error.
    Type '(e?: FormEvent<HTMLFormElement>) => void' is not assignable to type '(ev: NativeSyntheticEvent<NativeTouchEvent>) => void'.ts(2769)
index.d.ts(6926, 5): The expected type comes from property 'onPress' which is declared here on type 'IntrinsicAttributes & IntrinsicClassAttributes<Button> & Readonly<ButtonProps> & Readonly<{ children?: ReactNode; }>'
index.d.ts(6926, 5): The expected type comes from property 'onPress' which is declared here on type 'IntrinsicAt...

I understand that the handleSubmit function (e?: FormEvent<HTMLFormElement>) => void expects an event from a form submission (onSubmit attribute of a form element). Since there is no Form equivalent in RN, it complains about receiving the (ev: NativeSyntheticEvent<NativeTouchEvent>) => void from the RN Button's onPress attribute.

To get rid of the error, I used this workaround:

 <Button
              title="Do it !"
              color={colors.red}
              onPress={
                (handleSubmit as unknown) as (
                  ev: NativeSyntheticEvent<NativeTouchEvent>
                ) => void
              }
/>

I’m not satisfied with this solution and would like to know how to solve this typing error properly.

CodeSandbox: App.tsx:32

Can you help me?

2

The issue is caused by the mismatch between the expected event type of the handleSubmit function (FormEvent<HTMLFormElement>) and the actual event type received by the onPress attribute of the Button component (NativeSyntheticEvent<NativeTouchEvent>).

To solve this typing error properly, you can use the useCallback hook to create a memoized function that wraps the handleSubmit function and returns a new function with the expected event type.

Here’s an example of how to use useCallback:

import { useCallback } from 'react';
import { Button } from 'react-native';

// ...

const handleSubmit = (values: FormValues) => {
  // handle form submission
};

// ...

const handlePress = useCallback(() => {
  handleSubmit(values);
}, [values]);

return (
  // ...
  <Button title="Submit" onPress={handlePress} />
);

By using useCallback to create a memoized handlePress function, you can ensure that the function reference is stable across renders, while also providing the expected event type to the onPress attribute of the Button component.

CodeSandbox: App.tsx:34