How can I reach the variable which i named "global" from GlobalContext?

Question

I have a GlobalContext.js file. I want to reach this part by having a variable named "global" in my MainScreen. But it doesn't see it. Where could be my mistake?

I thought what I did was correct, but it doesnt work

Here is GlobalContext.js

import React, { createContext, useContext, useState } from 'react';
import HorizontalCircles from "../components/HorizontalDiscussion";
import HorizontalDiscussion from "../components/HorizontalDiscussion";


export const GlobalContext = createContext();

function GlobalContextManager(props) {

  const GetUsers = () => {
    const returnFromService = {
      "errorCode": -1,
      "data": {
        "colors": [
          {
            colorFirst:"red",
            colorSecond:"black",
          },
          {
            colorFirst:"pink",
            colorSecond:"gray",
          }
        ]
      }
    }; 

    if (returnFromService.errorCode === -1) {
      const returnFromGlobal = returnFromService.data.colors;
      return returnFromGlobal;
    } else {
      return returnFromService.errorCode;
    }
  }


  return (
    <GlobalContext.Provider value={{ GetUsers }}>
      {props.children}
    </GlobalContext.Provider>
  );
}

export default GlobalContextManager;

and here is the related part of MainScreen.js

import { GlobalContext } from '../../context/GlobalContext';

const MainScreen = ({ navigation }) => {

  const global = useContext(GlobalContext);

// here is skeleton
const [users, setUsers] = useState([
    <HorizontalCircles
      skeleton={true}
      key={0}
      colorFirst={'rgb(' + 100 + ',' + 100 + ',' + 100 + ')'}
      colorSecond={'rgb(' + 100 + ',' + 100 + ',' + 100 + ')'}
    />,
    <HorizontalCircles
      skeleton={true}
      key={1}
      colorFirst={'rgb(' + 100 + ',' + 100 + ',' + 100 + ')'}
      colorSecond={'rgb(' + 100 + ',' + 100 + ',' + 100 + ')'}
    />,
  ]);

 const getUsers = () => {

    console.log("users from global:",global.GetUsers());

    const g_users =  global.GetUsers(); // when i ctrl click on GetUsers() it says any...
    const tmpUsers = g_users.map((a,index) =>  <HorizontalCircles key={index} colorFirst={a.colorFirst} colorSecond={a.colorSecond} />)
       
    setTimeout(() => {
      setUsers(tmpUsers);
    }, 5000);

  }


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

and i wrote {users} somewhere in return in MainScreen.js

here is HorizontalCircles.js

import React from "react";
import { View, Text, TouchableOpacity, TouchableHighlight } from "react-native";

const HorizontalCircles = (props) => {

  return (
    // added TouchableHighlight to have more clickable area around circles
    <TouchableHighlight onPress={() => console.log("Circle is clicked")}>
      <View style={{ position: 'relative', height: 50, width: 50, borderColor: "white", borderWidth: 1, backgroundColor: props.colorFirst, elevation: 3, borderRadius: 25, marginHorizontal: 10, }} >
        <View style={{ position: 'absolute', right: 0, height: 15, width: 15, backgroundColor: props.colorSecond, borderRadius: 25, marginTop: 32 }} />
      </View>
    </TouchableHighlight>
    /* when i give elevation for the first View, the small circles lose a bit of their position */
  )
};

export default HorizontalCircles;

Answer 1

As per your comment,

GlobalContextManager must be used to or parent of MainScreen component. Since createContext has no default value when trying to access value with useContext, you will get undefined value.

Eg,

<GlobalContextManager>
   <MainScreen />
</GlobalContextManager>

Now, you can use the context in main screen component and you will get the value defined in the provider.

Answer 2

In my project I started using react context and ended up getting rid of it as it seems not adding that much value and actually introducing unnecessary technical debt. I suggest just having a normal JavaScript context object that you import wherever you need. You can set the properties of this object to be instances of other classes or just simple values for whatever you need to use across your application. Those values can be set into that object from wherever in your application. Just my 2 cents.