Cross Chain Tutorial Intro
Complete Project
Download the complete project on GitHub.
Project Setup
Open a terminal window, create a new folder for the project tutorial, e.g. mkdir cross-chain-tutorial
, and cd
into
the folder.
Now create separate folders to store contracts and scripts on L1 and L2. For now we will start with L1-governance folder.
mkdir L1-governance
The
L1-governance
code is a default Hardhat project used to deploy a contract on L1.
The L2-counter
code includes all ZKsync dependencies and configurations for L2.L1 Governance
cd
into theL1-governance
folder.
cd L1-governance
- Initialise and set up the L1 project.
npx hardhat init
Select the option Create a Typescript project and accept the defaults for everything else.
To interact with the ZKsync bridge contract using Solidity, you need
the ZKsync contract interface. There are two ways to get it:
- Import it from the
@matterlabs/zksync-contracts
npm package (preferred). - Download it from the contracts repo.
- Install the following dependencies:
npm i -D typescript ts-node @openzeppelin/contracts @matterlabs/zksync-contracts@beta @nomicfoundation/hardhat-ethers @typechain/ethers-v6 @typechain/hardhat typechain ethers dotenv
Create L1 Governance Contract
Make sure you're still in the
L1-governance
folder.The following Solidity code defines the Governance smart contract.
The constructor sets the contract creator as the single governor.
The callZkSync
function calls a transaction on L2 which can only be called by the governor.
- Remove the existing
/test
directory and any contracts that exist in/contracts
. - Create a new file called
Governance.sol
inside the emptycontracts
folder.
touch contracts/Governance.sol
- Copy/paste the code below into it.
L1-governance/contracts/Governance.sol
// SPDX-License-Identifier: Unlicense
pragma solidity ^0.8.13;
import { IBridgehub, L2TransactionRequestDirect } from '@matterlabs/zksync-contracts/contracts/l1-contracts/bridgehub/IBridgehub.sol';
contract Governance {
address public governor;
constructor() {
governor = msg.sender;
}
function callZkSync(
uint256 chainId,
address bridgeHubAddress,
address contractAddr,
bytes memory data,
uint256 gasLimit,
uint256 gasPerPubdataByteLimit,
uint256 cost
) external payable {
require(msg.sender == governor, 'Only governor is allowed');
IBridgehub zksyncBridgeHub = IBridgehub(bridgeHubAddress);
L2TransactionRequestDirect memory requestInput = L2TransactionRequestDirect(
chainId,
cost,
contractAddr,
0,
data,
gasLimit,
gasPerPubdataByteLimit,
new bytes[](0),
msg.sender
);
zksyncBridgeHub.requestL2TransactionDirect{ value: msg.value }(requestInput);
}
}