当 state 更改时，useEffect 不会重新加载子组件

Question

I have a react component structure like this:

In my table component, I have an option to trigger a modal that prompts user to give some input, which will then send a put request to the backend. In code it looks something like this:

const ParentContainer = (): JSX.Element => {
 const dataToPassDown = useSelector((state:IRootState) => selectData(state));
 return (
    <ParentComponent data={dataToPassDown}/>
  )
}


const ParentComponent = (props): JSX.Element => {
 const {data} = props;
 return (
   <MyHeader data = {data}/>
   <MyTable data = {data.tableData} />
 )  
}


const MyTable = (props): JSX.Element => {
 const {data} = props;
 const [inputFromModal, setInputFromModal] = useState("");
 const dispatch = useDispatch();
 
 useEffect(() => {
   dispatch(putRequest(inputFromModal);
 }, [inputFromModal]);

 return (
   <Modal visible={false} updateInputValue={setInputFromModal}/>
   <Table ... />
 )  
}

I want to refresh (only) the table component once the modal closes, but in this current setup, useEffect doesn't reload the table component when its state ( inputFromModal ) changes. Was I wrong in thinking that useEffect would reload the component when the state changed?

Answer 1

It is not part of useEffect to re-render your component. component will re-render when its state is changing or Parent component re-render.

By using useEffect , you tell React that your component needs to do something after render. (or in this case after every change of inputFromModal . it means that you are making put request every time inputFromModal is being changed.

For conclusion, in order to re-render your component, you need the data props to be updated by parent component.

Answer 2

You missed one point here, your table will be re-render only when the parent components re-render or the state of your MyTable Component changes , now the data which you are taking from props, set it in your state so that whenever that data changes your component will re-render

const MyTable = (props): JSX.Element => {
 const {data} = props;
 const [inputFromModal, setInputFromModal] = useState("");
 const [tableData, setTableData] = useState();
 const dispatch = useDispatch();

 useEffect(() => {
   setTableData(data)
 }, [data]);
 
 useEffect(() => {
   dispatch(putRequest(inputFromModal);
 }, [inputFromModal]);

 return (
   <Modal visible={false} updateInputValue={setInputFromModal}/>
   <Table ... />
 )  
}