Skip to main content

Solidity Package

Quickly integrate cross-chain functionalities into your projects with VIA Labs' Solidity package.

info

📘 If you just want to try us out quickly, follow our Cross-Chain Token or Cross-Chain NFT guides to launch your own cross-chain assets in minutes.

Installation#

Start by installing the package in your project:

npm install https://github.com/VIALabs-io/npm-contracts

Contract Configuration#

To enable cross-chain communication in your application, you need to implement two key functions:

  1. _sendMessage() - Sends data to another blockchain
  2. _processMessage() - Receives and processes data from another blockchain

Simple Code Example#

Here's a straightforward example of a cross-chain ERC20 token:

// SPDX-License-Identifier: MITpragma solidity 0.8.17;
import "@vialabs-io/npm-contracts/MessageClient.sol";import "@openzeppelin/contracts/token/ERC20/extensions/ERC20Burnable.sol";
contract HelloERC20 is ERC20Burnable, MessageClient {    constructor() ERC20("HelloERC20", "HELLO") {        _mint(msg.sender, 1_000_000 ether);    }
    function bridge(uint _destChainId, address _recipient, uint _amount) external onlyActiveChain(_destChainId) {        // burn tokens        _burn(msg.sender, _amount);
        // send cross chain message        _sendMessage(_destChainId, abi.encode(_recipient, _amount));    }
    function _processMessage(uint _sourceChainId, uint /* _sourceMsgSender */, bytes calldata _data) internal virtual override {        // decode message        (address _recipient, uint _amount) = abi.decode(_data, (address, uint));
        // mint tokens        _mint(_recipient, _amount);    }}

Key Functions Explained#

_sendMessage()#

The _sendMessage() function packages and sends data to another blockchain.

function _sendMessage(uint destinationChainId, bytes memory data) internal returns (uint txId);

Parameters:

  • destinationChainId: The ID of the chain to send the message to
  • data: The message data to be sent (encoded using abi.encode())

Returns:

  • txId: A unique transaction ID for the message

_processMessage()#

The _processMessage() function receives and processes data from another blockchain. You must override this function in your contract to handle incoming messages.

function _processMessage(uint _sourceChainId, uint _sourceMsgSender, bytes calldata _data) internal virtual;

Parameters:

  • _sourceChainId: ID of the source chain from where the message is coming
  • _sourceMsgSender: Address of the sender on the source chain (can be ignored in many cases)
  • _data: Message data (decode using abi.decode())

Modifiers#

The MessageClient contract provides useful modifiers:

  • onlyActiveChain(uint chainId): Ensures the destination chain is active and configured
  • onlySelf(address sender, uint sourceChainId): Validates that the message is from a trusted source

Configuration#

After deploying your contracts, you need to configure them to communicate with each other. This is done using the configureClient() function:

const { ethers } = require('ethers');const chainsConfig = require('./config/chains');const { MessageClientABI } = require('./message/abi');
async function configureContract() {    // Configuration Parameters    const rpcUrl = 'https://mainnet.infura.io/v3/YOUR_INFURA_API_KEY';     const privateKey = '0xYOUR_PRIVATE_KEY';    const contractAddress = '0xabcd...1234'; // Your deployed contract address
    // Initialize ethers with provider and signer    const provider = new ethers.providers.JsonRpcProvider(rpcUrl);    const signer = new ethers.Wallet(privateKey, provider);
    // Instantiate the contract    const myContract = new ethers.Contract(contractAddress, MessageClientABI, signer);
    try {        const chains = [5, 11155111, 17000]; // Desired chain IDs        const endpoints = ['0x000000','0x000000','0x000000']; // Your deployed instances on each chain        const confirmations = [12, 6, 6]; // Desired confirmation counts for each chain
        // Configure the client with MessageV3 address and chain data        const tx = await myContract.configureClient(            chainsConfig[hre.network.config.chainId].message, // Message contract address            chains,             endpoints,             confirmations        );
        console.log('Transaction sent:', tx.hash);        await tx.wait();        console.log('Chains configured successfully.');    } catch (error) {        console.error('An error occurred during configuration:', error);    }}
// Execute the configurationconfigureContract();

Next Steps#

Ready to build more complex cross-chain applications? Check out our examples:

Need help? Join our Discord community for support and discussions.