UseState renders me the previous state-CodePudding

I have two inputs that change the text of a P tag at the same time, but the problem is that the render that shows me is always the previous value that was saved. I understand that I have to use a useEffect to render the component again and show the current value, but in the inputs handleChange if or if I need to send to the SetState that changes the text, the value that was saved in the initialValue. Until now I am learning React and I have already tried a lot of things, but nothing works for me, how could I implement the useEffect in this case? Thank you very much for the help.

const initialValue = {
  input1: 0,
  input2: 0,
};

const TestState = () => {
  const [obj, setObj] = useState(initialValue);
  const [textChange, setTextChange] = useState("-");

  useEffect(() => {}, [obj]);

  const handleChange = (e) => {
    setObj({ ...obj, [e.target.name]: e.target.value });
    //Basically I need to do this -> setTextChange(e.target.value), but with the value stored in the initialValue.
    setTextChange(e.target.name === "input1" ? obj.input1 : obj.input2);
  };

  return (
    <div>
      <form>
        <input type="text" name="input1" onChange={handleChange} />
        <input type="text" name="input2" onChange={handleChange} />
      </form>
      <p>{textChange}</p>
    </div>
  );
};

https://codesandbox.io/s/practical-mahavira-pd94p?file=/src/TestState.js

CodePudding user response：

The setter you get from useState (i.e. setObj) does not immediately alter the value/state of the object under control. The update occurs before the next render(). That is why your obj object appears to be stale.

Note, you don't need to replace the obj object itself, you're just updating its contents. You could just do this:

const [obj] = useState(initialValue);
...

const handleChange = (e) => {
  //setObj({ ...obj, [e.target.name]: e.target.value });
  obj[e.target.name] = e.target.value;
  setTextChange(e.target.name === "input1" ? obj.input1 : obj.input2);
}