A mobile App for ShellHacks using React Native with Expo, NodeJS, and MongoDB database.
This project was bootstrapped with expo init.
Below you'll find information about performing common tasks. The most recent version of this guide is available here.
Updating the react-native-scripts dependency of your app should be as simple as bumping the version number in package.json and reinstalling your project's dependencies.
Upgrading to a new version of React Native requires updating the react-native, react, and expo package versions, and setting the correct sdkVersion in app.json. See the versioning guide for up-to-date information about package version compatibility.
Runs your app in development mode.
Open it in the Expo app on your phone to view it. It will reload if you save edits to your files, and you will see build errors and logs in the terminal.
Sometimes you may need to reset or clear the React Native packager's cache. To do so, you can pass the --reset-cache flag to the start script:
npm start -- --reset-cache
## Customizing App Display Name and Icon
You can edit `app.json` to include [configuration keys](https://docs.expo.io/versions/latest/guides/configuration.html) under the `expo` key.
To change your app's display name, set the `expo.name` key in `app.json` to an appropriate string.
To set an app icon, set the `expo.icon` key in `app.json` to be either a local path or a URL. It's recommended that you use a 512x512 png file with transparency.
## Environment Variables
You can configure some of Create React Native App's behavior using environment variables.
### Configuring Packager IP Address
When starting your project, you'll see something like this for your project URL:
exp://192.168.0.2:19000
The "manifest" at that URL tells the Expo app how to retrieve and load your app's JavaScript bundle, so even if you load it in the app via a URL like `exp://localhost:19000`, the Expo client app will still try to retrieve your app at the IP address that the start script provides.
In some cases, this is less than ideal. This might be the case if you need to run your project inside of a virtual machine and you have to access the packager via a different IP address than the one which prints by default. In order to override the IP address or hostname that is detected by Create React Native App, you can specify your own hostname via the `REACT_NATIVE_PACKAGER_HOSTNAME` environment variable:
Mac and Linux:
REACT_NATIVE_PACKAGER_HOSTNAME='my-custom-ip-address-or-hostname' npm start
Windows:
set REACT_NATIVE_PACKAGER_HOSTNAME='my-custom-ip-address-or-hostname' npm start
The above example would cause the development server to listen on `exp://my-custom-ip-address-or-hostname:19000`.
## Adding Flow
Flow is a static type checker that helps you write code with fewer bugs. Check out this [introduction to using static types in JavaScript](https://medium.com/@preethikasireddy/why-use-static-types-in-javascript-part-1-8382da1e0adb) if you are new to this concept.
React Native works with [Flow](http://flowtype.org/) out of the box, as long as your Flow version matches the one used in the version of React Native.
To add a local dependency to the correct Flow version to a Create React Native App project, follow these steps:
1. Find the Flow `[version]` at the bottom of the included [.flowconfig](.flowconfig)
2. Run `npm install --save-dev [email protected]` (or `yarn add --dev [email protected]`), where `x.y.z` is the .flowconfig version number.
3. Add `"flow": "flow"` to the `scripts` section of your `package.json`.
4. Add `// @flow` to any files you want to type check (for example, to `App.js`).
Now you can run `npm run flow` (or `yarn flow`) to check the files for type errors.
You can optionally use a [plugin for your IDE or editor](https://flow.org/en/docs/editors/) for a better integrated experience.
To learn more about Flow, check out [its documentation](https://flow.org/).
## Troubleshooting
### Networking
If you're unable to load your app on your phone due to a network timeout or a refused connection, a good first step is to verify that your phone and computer are on the same network and that they can reach each other. Create React Native App needs access to ports 19000 and 19001 so ensure that your network and firewall settings allow access from your device to your computer on both of these ports.
Try opening a web browser on your phone and opening the URL that the packager script prints, replacing `exp://` with `http://`. So, for example, if underneath the QR code in your terminal you see:
exp://192.168.0.1:19000
Try opening Safari or Chrome on your phone and loading
and
If this works, but you're still unable to load your app by scanning the QR code, please open an issue on the [Create React Native App repository](https://github.com/react-community/create-react-native-app) with details about these steps and any other error messages you may have received.
If you're not able to load the `http` URL in your phone's web browser, try using the tethering/mobile hotspot feature on your phone (beware of data usage, though), connecting your computer to that WiFi network, and restarting the packager.
### iOS Simulator won't open
If you're on a Mac, there are a few errors that users sometimes see when attempting to `npm run ios`:
* "non-zero exit code: 107"
* "You may need to install Xcode" but it is already installed
* and others
There are a few steps you may want to take to troubleshoot these kinds of errors:
1. Make sure Xcode is installed and open it to accept the license agreement if it prompts you. You can install it from the Mac App Store.
2. Open Xcode's Preferences, the Locations tab, and make sure that the `Command Line Tools` menu option is set to something. Sometimes when the CLI tools are first installed by Homebrew this option is left blank, which can prevent Apple utilities from finding the simulator. Make sure to re-run `npm/yarn run ios` after doing so.
3. If that doesn't work, open the Simulator, and under the app menu select `Reset Contents and Settings...`. After that has finished, quit the Simulator, and re-run `npm/yarn run ios`.
### QR Code does not scan
If you're not able to scan the QR code, make sure your phone's camera is focusing correctly, and also make sure that the contrast on the two colors in your terminal is high enough. For example, WebStorm's default themes may [not have enough contrast](https://github.com/react-community/create-react-native-app/issues/49) for terminal QR codes to be scannable with the system barcode scanners that the Expo app uses.
If this causes problems for you, you may want to try changing your terminal's color theme to have more contrast, or running Create React Native App from a different terminal. You can also manually enter the URL printed by the packager script in the Expo app's search bar to load it manually.
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