antd getfieldvalue undefined

const [form] = useForm();
const [fieldValue, setFieldvalue](undefined)

const onValuesChange = ({fieldName}) => {
    if(!fieldValue && fieldName) {
        setFieldvalue(fieldName)
     }
}

return (
    <Form
        form={form}
        onValuesChange={onValuesChange}
    >
        ....
    </Form>
)