Context

• Neynar makes it possible to programmatically create Farcaster accounts: https://docs.neynar.com/docs/how-to-create-a-new-farcaster-account-with-neynar
• Neynar pays the fee to Farcaster protocol so the user experience is uninterrupted. Developer can choose to charge the user however they want, Neynar adds fees to monthly invoice.

When onboarding users with embedded wallets, there are added steps needed that the above guide doesn’t list out yet. While we work on updating that guide, below unofficial steps from JP who onboarded users on their app using Neynar APIs and Privy wallets. Shoutout to JP Franeto for the write up! 🪐

<aside> 💡

Disclaimer: Neynar team hasn’t run the code below so use at your own discretion. We will put up our version on the official guide soon.

</aside>

Privy x Neynar Integration: Creating a New FID from a User's Embedded Wallet

Overview

This documentation outlines the process for creating a new Farcaster ID (FID) using the Privy x Neynar integration. It details the frontend and backend implementations required to register a user through their embedded wallet, which is created using Privy.

Source Code

The complete implementation can be found in the following repositories:

• Frontend Implementation (Expo App): https://github.com/ankylat/anky/tree/main/app
• Backend Implementation (Farcaster Anky Bot): https://github.com/jpfraneto/farcaster.anky.bot/blob/main/src/index.tsx

Frontend Implementation

Relevant CreateAccountModal Component

The CreateAccountModal is a React Native component that is used to register a new user on Farcaster.

Creating the Farcaster account

import { usePrivy } from "@privy-io/expo";
import { useSmartWallets } from "@privy-io/expo/smart-wallets";

const CreateAccountModal = () => {
  const { client } = useSmartWallets();
  const { user, isReady } = usePrivy();

  const handleCreateAccount = async () => {
    try {
      if (user && client) {
        const smartWallet = user.linked_accounts.find(
          (account) => account.type === "smart_wallet"
        );

        if (!smartWallet?.address) {
          throw new Error("Smart wallet not found");
        }

        const { data: payload } = await axios.post(
          "<https://farcaster.anky.bot/create-new-fid>",
          {
            user_wallet_address: smartWallet?.address,
          }
        );

        const signature = await client.signTypedData({
          account: client.account,
          domain: {
            name: "Farcaster ID Registry",
            version: "1",
            chainId: 10, // Optimism
            verifyingContract: "0x00000000fc6c5f01fc30151999387bb99a9f489b", // ID_REGISTRY_ADDRESS
          },
          types: {
            Transfer: [
              { name: "fid", type: "uint256" },
              { name: "to", type: "address" },
              { name: "nonce", type: "uint256" },
              { name: "deadline", type: "uint256" },
            ],
          },
          message: {
            fid: payload.new_fid,
            to: smartWallet.address,
            nonce: payload.nonce,
            deadline: payload.deadline,
          },
        });

        const res = await axios.post(
          "<https://farcaster.anky.bot/create-new-fid-signed-message>",
          {
            deadline: Number(payload.deadline),
            address: wallet.account?.address,
            fid: payload.new_fid,
            signature,
            user_id: ankyUser?.id,
          }
        );

        console.log("Registration successful:", res.data);
        onClose();
      }
    } catch (error) {
      console.error("Error creating Farcaster account:", error);
      setError(error.message || "Failed to create Farcaster account");
    }
  };
};