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Setting up your application

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Prerequisites

  • Node.js: A JavaScript runtime built on Chrome’s V8 JavaScript engine. Ensure you have Node.js installed on your system.
  • Expo Go: Install Expo Go on your phone

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Cloning the repo

Clone the repo from GitHub using the following command and open it up in your favourite code editor using the following commands: 
npx degit https://github.com/neynarxyz/farcaster-examples/tree/main/wownar-react-native react-native-siwn
cd react-native-siwn
Once you’ve cloned your repo we can start installing the packages and setting up the env variables!

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Server

1

Navigate to server directory

Navigate to the server directory
cd server
2

Install Project Dependencies

Based on the package manager run one of the following commands to install all required dependencies:
npm i
3

Configure Environment Variables

Copy the example environment file:
cp .env.example .env
Edit .env to add your NEYNAR_API_KEY and NEYNAR_CLIENT_ID. You can find them in your dashboard
4

Start the server

Start the server:
npm run start

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Client

Open new terminal
1

Navigate to client directory

Navigate to the client directory
cd client
2

Install Project Dependencies

Based on the package manager run one of the following commands to install all required dependencies:For yarn
yarn install
For npm
npm install
3

Configure Environment Variables

Copy the example environment file:
cp .env.example .env
4

Start the app

Make sure your phone and computer is connected to the same networkFor yarn
yarn start
For npm
npm run start
you’ll see a QR Code
5

Run App

Open the Expo Go app on your phone and scan the QR Code. You should now be able to see a button to sign in with neynar in your app!

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How does it work?

You’re probably wondering how it all works, so let’s break it down!

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Server

In our server, we have 3 API routes, you can take a look at them in server/index.js:
  • /get-auth-url (GET): This API route gets the authorization URL using the fetchAuthorizationUrl function from the neynar client.
  • /user (GET): This API route takes in the fid as a query parameter and returns the user data like display name and pfp url using the fetchBulkUsers function.
  • /cast (POST): This API route takes in the signer UUID and text in the body and publishes the cast on behalf of the user using the publishCast function.

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Client

On the client side, we use the NeynarSigninButton component from the @neynar/react-native-signin package and pass in a bunch of props like fetchAuthorizationUrl, successCallback, errorCallback, and redirectUrl.
  • For fetchAuthorizationUrl we fetch the url from our server and then pass it.
  • For successCallback we are creating a function Context/AppContext.ts that fetches the user info from the backend and safely stores it.
  • For errorCallBack we simply just console log the error.
  • For redirectURL we are using a URL of the format exp://${COMPUTER_IP_ADDRESS}:8081. The COMPUTER_IP_ADDRESS is the one you added in your .env file
  • There are also a lot of customisation options that you can find commented out in the Signin.tsx file.

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Conclusion

This guide taught us how to add sign-in with neynar to a React native app, check out the GitHub repository. Lastly, make sure to sure what you built with us on Farcaster by tagging @neynar and if you have any questions, reach out to us on warpcast or Telegram!