Example: Hello World

Here is a hello-world example that sends and receives cross-chain messages with simple logic:
Users call sendMessage on the source chain to send a number.
The receiver side implements _handleMessage to receive and emit the number and sender at the destination chain.
​Source code at GitHub. 
// A HelloWorld test example for basic cross-chain message passing
contract MsgTest is MessageApp {
    event MessageReceived(
        uint64 srcChainId,
        address srcContract,
        address sender,
        uint64 number
    );
​
    constructor(IMessageBridge _messageBridge) MessageApp(_messageBridge) {}
​
    // called by user on source chain to send cross-chain messages
    function sendMessage(
        uint64 _dstChainId,
        address _dstContract,
        uint64 _number
    ) external {
        bytes memory message = abi.encode(msg.sender, _number);
        _sendMessage(_dstChainId, _dstContract, message);
    }
​
    // called by MessageBridge on destination chain to receive cross-chain messages
    function _handleMessage(
        uint64 _srcChainId,
        address _srcContract,
        bytes calldata _message,
        address // execution
    ) internal override {
        (address sender, uint64 number) = abi.decode((_message), (address, uint64));
        require(number != 1000, _abortReason("test abort"));
        require(number != 1001, "test revert");
        emit MessageReceived(_srcChainId, _srcContract, sender, number);
    }
}
Last modified 4mo ago