Material-UI and Redux-form not styling when being mapped - reactjs

Question

I've created this codesandbox - https://codesandbox.io/s/pk8p4lvl90
I can implement the material-ui instructions (https://redux-form.com/7.2.2/examples/material-ui/) fine without the mapping mechanism, but as soon as I apply the mapping I can't get the material-ui to implement the look for a textfield.
In my example I have commented out the code I have tried that works without mapping being involved.
Form -
<form onSubmit={handleSubmit}>
<div>
{/* <Field
name="firstName"
component={renderTextField}
label="First Name"
/>*/}
<FieldArray
name="firstName"
component={renderTextField}
label="First Name"
/>
</div>
</form>
TextField Render -
const renderTextField = ({ fields, input, label }) => (
<div>
{fields.map((newIntel, index) => (
{/* <TextField
name={newIntel}
key={index}
label={label}
placeholder={label}
component="input"
placeholder={label}
label={label} /> */}
<Field
name={newIntel}
key={index}
label={label}
placeholder={label}
component="input"
placeholder={label}
label={label}
/>
))}
<div
variant="fab"
color="primary"
className="jr-fab-btn"
aria-label="add"
onClick={() => fields.push()}
>
Click me
</div>
</div>
);

Answer 1

In order to use redux-form features with material-ui look, you need use redux-form's input component with render function that will return material-ui's component with appropriate props. You started doing so, but renderTextField should look a little bit differently, e.g.:
const renderTextField = ({
input,
label,
meta: { touched, error },
...custom
}) => (
<TextField
hintText={label}
floatingLabelText={label}
errorText={touched && error}
{...input}
{...custom}
/>
)
Having this, you can reuse it in, let's say renderForm function:
const renderForm = ({ fields, input, label }) => (
<div>
{fields.map((newIntel, index) => (
<Field
...
component={renderTextField}
...
/>
))}
...
</div>
);
That's based on what I've found in the redux-form Docs you linked. Take another look there as well, it's well described there as well.