Refactor: Extract Hardcoded Url into app config

app/README.md

@@ -9,13 +9,20 @@ Please follow instructions from the [expo website](https://expo.io/learn) to see
 npm install
 ```
 
-Then update the IP address in `components/Server.tsx` to point to the IP address of the computer running the local server:
-```js
-3: const URL = "http://192.168.1.29:8080";
-```
+Then update the IP address to point to the IP address of the computer running the local server by either:
+
+  1. Using environment variable `AR_CP_SERVER_URL` or
+  2. in the `serverUrl` field in [app.json](/app/app.json)
+
+     eg `"serverUrl": "http://192.168.1.29:8080"`
 
 ## Run
 
+If you have supplied the environment variable `AR_CP_SERVER_URL`
+```bash
+AR_CP_SERVER_URL="http://<ip>:<port>" npm start
+```
+else
 ```bash
 npm start
 ```

app/app.config.js

@@ -0,0 +1,7 @@
+export default ({config}) => {
+  return {
+    extra: {
+      "serverUrl": process.env.AR_CP_SERVER_URL || config.serverUrl
+    }
+  }
+}

app/app.json

@@ -15,6 +15,7 @@
       "resizeMode": "contain",
       "backgroundColor": "#ffffff"
     },
+    "serverUrl": "http://<ip>:<port>",
     "updates": {
       "fallbackToCacheTimeout": 0
     },

app/components/Server.tsx

@@ -1,6 +1,7 @@
 import Base64 from "./Base64";
+import Constants from 'expo-constants';
 
-const URL = "http://192.168.1.29:8080";
+const URL = Constants.manifest.extra.serverUrl;
 
 function arrayBufferToBase64(buffer: ArrayBuffer) {
   let binary = "";