antd getfieldvalue undefined

1const [form] = useForm();
2const [fieldValue, setFieldvalue](undefined)
3
4const onValuesChange = ({fieldName}) => {
5    if(!fieldValue && fieldName) {
6        setFieldvalue(fieldName)
7     }
8}
9
10return (
11    <Form
12        form={form}
13        onValuesChange={onValuesChange}
14    >
15        ....
16    </Form>
17)
18