react native - Calling locally hosted server from Expo App

Question

I am creating a react-native app and one of the components I have created contains a property which is populated through data coming from an http request.

Right now I am hosting the server from my laptop, however I am testing the app on my phone using the Expo app. Since these are two separate devices, the http://localhost:3000 calls are not working and thus I can not tell whether or not my component is properly working.

Is there any way for me to run the server on my laptop and set it up so that the http requests from within the Expo app reach the server?

Answer 1

You can get the IP address at runtime using the Expo manifest:

import Constants from "expo-constants";
const { manifest } = Constants;

const api = (typeof manifest.packagerOpts === `object`) && manifest.packagerOpts.dev
  ? manifest.debuggerHost.split(`:`).shift().concat(`:3000`)
  : `api.example.com`;

This will set api constant to the address of your local development machine in development mode and to whatever address you use in production. Note that apps deployed through App Store / Play Store seems to have packagerOpts undefined. That's why we have additional typeof condition. In that case we assume it's production build.

More about the manifest here: https://docs.expo.io/versions/latest/workflow/how-expo-works/#expo-development-server