React-native Formik setFieldValue - react-native

Question

Here is a simplified version of my code.
Notice the setFieldValue_ and this.setFieldValue_ = setFieldValue;
This code works fine, I'm able to get the output when submit button is clicked.
I'm actually wondering if this is the right way to do it? If not, can you point me to the right direction? Also what is this method called? (assigning class variable to some function and use it within another function)
class MyComponent extends React.Component {
setFieldValue_;
someFunction() {
this.setFieldValue_("name", value);
}
render() {
return (
<Formik
initialValues={{
something: ""
}}
onSubmit={values => console.log(values)}
>
{({
setFieldValue,
}) => {
this.setFieldValue_ = setFieldValue;
<ThirdPartyCustomComponent onChange={this.someFunction} />
}}
</Formik>
}
}

Answer 1

I would personally have the onChange simply call formik set field value there and then rather than using different functions. Strictly speaking you don't want to set the value like that because every re-render is setting the value again.
I would also recommend looking at custom formik inputs using the useField hook - https://jaredpalmer.com/formik/docs/api/useField. This will allow you to write a small wrapper around your third party component and formik. Noticing you have used a class based component you may want to do some short reading into react hooks before throwing yourself into using useField.
Docs example:
const MyTextField = ({ label, ...props }) => {
const [field, meta, helpers] = useField(props);
return (
<>
<label>
{label}
<input {...field} {...props} />
</label>
{meta.touched && meta.error ? (
<div className='error'>{meta.error}</div>
) : null}
</>
);
};