How to setState with fetched data in React

Question

I need to setState with an object that I'm getting from a redux store. The problem is when I call setState in my component I am getting undefined. Any idea on how to set a default value of state with fetched data?

Here is my component:

import React, { useEffect, Fragment, useState } from 'react';
import { useSelector, useDispatch } from 'react-redux';

const contactDetails = useSelector((state) => state.contactDetails)

const upFields = contactDetails?.contact?.data?.fields


const [contact, setContact] = useState({
    fields:  upFields <---- this is returning undefined.. The name is correct, but maybe setState is running too fast? 
  })
  

console.log(contact) <---- this shows {fields: undefined}



console.log(upFields) <---- this console.logs just fine

Answer 1

you use useEffect() and trigger it using the object

useEffect(()=>{
  setContact(fetched_data)
}, [fetched_data]) // <-- data array will trigger every time this data change

you can trigger it on first component mount with

useEffect(()=>{
  setContact(fetched_data)
}, []) // <-- empty array will only trigger once