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USDC provides the ability to transfer digital dollars over public blockchains using smart contracts. The USDC smart contract allows you to send, receive, and store digital dollars onchain with a wallet. This quickstart guide provides step-by-step instructions to build a React app that allows users to connect their wallet and send USDC transactions over Sonic Blaze Testnet.

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Prerequisites

Before you begin, make sure you have:
  • Installed Node.js and npm. You can download and install Node.js from Nodejs.org. npm comes with Node.js.
  • Installed Metamask
  • Some Sonic testnet tokens in your wallet to cover transaction fees. You can use the Sonic Faucet.
  • Testnet USDC tokens in your wallet for the transfer. You can use the CCTP Sample App to move testnet USDC from Ethereum Sepolia to Sonic Blaze.

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Contract address

You will need the following contract address for the USDC token on Sonic Blaze Testnet:

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Part 1: Set up your project

Perform the following installation and setup steps:
  1. Create a new project directory and initialize it with npm:
Shell
mkdir usdc-transfer-app
cd usdc-transfer-app
npm init -y
  1. Install the required dependencies:
Shell
npm install react@latest \
  react-dom@latest \
  @types/react@latest \
  @types/react-dom@latest \
  @vitejs/plugin-react@latest \
  typescript@latest \
  vite@latest \
  viem@latest
  1. Verify the installation by checking the package.json file. It should look like this:
JSON
{
  "name": "usdc-transfer-app",
  "version": "1.0.0",
  "main": "index.js",
  "scripts": {
    "dev": "vite",
    "build": "vite build",
    "preview": "vite preview"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "description": "",
  "dependencies": {
    "@types/react": "^19.1.2",
    "@types/react-dom": "^19.1.2",
    "@vitejs/plugin-react": "^4.4.1",
    "react": "^19.1.0",
    "react-dom": "^19.1.0",
    "typescript": "^5.8.3",
    "viem": "^2.28.0",
    "vite": "^6.3.2"
  }
}
If your package.json file does not contain the scripts section, copy and paste it from the above code into your file. Test that you can run the project with the command:
Shell
npm run dev

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Part 2: Import clients and set up helpers

Perform the following steps to import code and set up helpers for the application.
  1. Create a new file src/client.ts and copy the following code into it. This code imports required libraries and sets up the network configuration.
Typescript
import { http, createPublicClient, createWalletClient, custom } from "viem";
import { sonicBlazeTestnet } from "viem/chains";

declare global {
  interface Window {
    ethereum: any;
  }
}

export const publicClient = createPublicClient({
  chain: sonicBlazeTestnet,
  transport: http(),
});

export const walletClient = createWalletClient({
  chain: sonicBlazeTestnet,
  transport: custom(window.ethereum),
});
  1. Define the USDC testnet token contract details in a new file src/constants.ts. This file contains the contract address and Application Binary Interface (ABI) for the USDC token on Sonic Blaze.
Typescript
export const USDC_CONTRACT_ADDRESS =
  "0xA4879Fed32Ecbef99399e5cbC247E533421C4eC6";

export const USDC_ABI = [
  {
    constant: false,
    inputs: [
      { name: "_to", type: "address" },
      { name: "_value", type: "uint256" },
    ],
    name: "transfer",
    outputs: [{ name: "", type: "bool" }],
    type: "function",
  },
  {
    constant: true,
    inputs: [{ name: "_owner", type: "address" }],
    name: "balanceOf",
    outputs: [{ name: "balance", type: "uint256" }],
    type: "function",
  },
];

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Part 3: Create the main application component

The following steps create the main application component and show the steps to connect a wallet and transfer USDC.
  1. Create a new file src/App.tsx and copy the following code into it. This code contains the main application component that allows users to connect their wallet and transfer USDC.
Typescript
import React, { useEffect, useState } from 'react';
import { publicClient, walletClient } from './clients';
import { USDC_CONTRACT_ADDRESS, USDC_ABI } from './constants';
import { type Address, encodeFunctionData, type Hash, type TransactionReceipt, stringify } from 'viem';

function USDCApp() {
  const [account, setAccount] = useState<Address>();
  const [balance, setBalance] = useState<string>();
  const [hash, setHash] = useState<Hash>();
  const [receipt, setReceipt] = useState<TransactionReceipt>();
  const [recipient, setRecipient] = useState<string>('');
  const [amount, setAmount] = useState<string>('');
  const [isTransferring, setIsTransferring] = useState(false);

  const addressInput = React.createRef<HTMLInputElement>();
  const valueInput = React.createRef<HTMLInputElement>();

  // Fetch USDC balance
  const fetchBalance = async (address: Address) => {
    const balance = await publicClient.readContract({
      address: USDC_CONTRACT_ADDRESS,
      abi: USDC_ABI,
      functionName: "balanceOf",
      args: [address],
    }) as bigint;
    setBalance((Number(balance) / 10 ** 6).toFixed(2));
  };

  // Connect Wallet
  const connect = async () => {
    const [address] = await walletClient.requestAddresses();
    setAccount(address);
    fetchBalance(address);
  };

  // Transfer USDC
  const transferUSDC = async (e: React.FormEvent) => {
    e.preventDefault();
    if (!account || !recipient || !amount) return;

    try {
      setIsTransferring(true);
      const amountInWei = BigInt(Math.floor(Number(amount) * 10 ** 6));

      const { request } = await publicClient.simulateContract({
        account,
        address: USDC_CONTRACT_ADDRESS,
        abi: USDC_ABI,
        functionName: 'transfer',
        args: [recipient as Address, amountInWei],
      });

      const hash = await walletClient.writeContract(request);
      setHash(hash);

      const receipt = await publicClient.waitForTransactionReceipt({ hash });
      setReceipt(receipt);

      // Refresh balance after transfer
      await fetchBalance(account);

      // Clear form
      setRecipient('');
      setAmount('');
    } catch (error) {
      console.error('Transfer failed:', error);
    } finally {
      setIsTransferring(false);
    }
  };

  return (
    <div>
      <h1>USDC Transfer Sample App</h1>
      {account ? (
        <>
          <p><strong>Connected Wallet:</strong> {account}</p>
          <p><strong>USDC Balance:</strong> {balance ? `${balance} USDC` : "Fetching..."}</p>

          <form onSubmit={transferUSDC} style={{ marginTop: '20px' }}>
            <div style={{ marginBottom: '10px' }}>
              <label>
                Recipient Address:
                <input
                  type="text"
                  value={recipient}
                  onChange={(e) => setRecipient(e.target.value)}
                  placeholder="0x..."
                  style={{ marginLeft: '10px', width: '300px' }}
                />
              </label>
            </div>
            <div style={{ marginBottom: '10px' }}>
              <label>
                Amount (USDC):
                <input
                  type="number"
                  value={amount}
                  onChange={(e) => setAmount(e.target.value)}
                  placeholder="0.00"
                  step="0.01"
                  min="0"
                  style={{ marginLeft: '10px' }}
                />
              </label>
            </div>
            <button type="submit" disabled={isTransferring}>
              {isTransferring ? 'Transferring...' : 'Transfer USDC'}
            </button>
          </form>

          {hash && (
            <div style={{ marginTop: '20px' }}>
              <p><strong>Transaction Hash:</strong> {hash}</p>
            </div>
          )}

          {receipt && (
            <div style={{ marginTop: '10px' }}>
              <p><strong>Transaction Status:</strong> {receipt.status === 'success' ? 'Success' : 'Failed'}</p>
            </div>
          )}
        </>
      ) : (
        <button onClick={connect}>Connect Wallet</button>
      )}
    </div>
  );
}

export default USDCApp;
  1. Create your application entrypoint by creating a new file src/main.tsx and copying the following code into it. This code sets up the React application and renders the USDCApp component.
Typescript
import React from 'react';
import ReactDOM from 'react-dom/client';
import USDCApp from './App';

ReactDOM.createRoot(document.getElementById('root')!).render(
  <React.StrictMode>
    <USDCApp />
  </React.StrictMode>
);
  1. Create a new file index.html in the root directory and copy the following code into it. This code sets up the HTML structure for the application.
HTML
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>USDC Transfer Sample App</title>
  </head>
  <body>
    <div id="root"></div>
    <script type="module" src="/src/main.tsx"></script>
  </body>
</html>
  1. Run your application using the following command:
Shell
npm run dev
You can open http://localhost:5173 in your browser to view the application.

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Connecting your wallet

  • In the application, click the Connect Wallet button. This will prompt you to connect your wallet using Metamask.
  • Select your Sonic wallet address from the available options.
  • Approve the connection request in Metamask.

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Transferring USDC

  • In the app, enter the amount of USDC to send, and the recipient’s wallet address.
  • Click Send Tokens
  • Review the transaction details in the Metamask pop-up and approve the transaction.
  • Wait for the transaction to be confirmed. The app displays the transaction hash and status once the transfer is complete.
  • You can check the transaction status on the Sonic Explorer.
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