返回未定义的 Redux 存储 state 在 useEffect() function

Question

My Redux store state return undefined in useEffect hook. If I remove empty array [] in useEffect , my Redux store return true value but very much and sometimes executed in an endless loop!

 useEffect(() => {
    store.subscribe(() => {
      setNodeProperties({
        positionX: store.getState().schemaViewer.positionX,
        positionY: store.getState().schemaViewer.positionY,
      });
        console.log(nodeProperties);
    });
  }, []);

Answer 1

The problem is setNodeProperties will queue up the change for nodeProperties and it won't happen right away because it is asynchronous. So I would try to run a side effect once nodeProperties is changing. You can have multiple useEffect hooks in your component.

Try as the following:

useEffect(() => {
   console.log(nodeProperties);
}, [nodeProperties]);

In this way you are capturing changes for nodeProperties and run the logging step only then. Suggested read is Using the Effect Hook .

I hope this helps!