Deploy your gApp

This guide shows you how to deploy and interact with a smart contract on PlayChain. This requires some preexisting knowledge of how to develop EVM smart contracts in general.

Following the below instructions will allow you to deploy and interact with a smart contract on PlayChain in less than 5 minutes. It will help you get familiar with the zkSync development toolbox which can be used to develop PlayFi projects.

This is what we're going to do:

  • Fund your wallet with PlayChain testnet ETH.

  • Use zksync-cli to scaffold a new project.

  • Build a smart contract that stores a greeting message and deploy it to PlayChain Albireo testnet.

  • Run a script to retrieve and update the greeting message using zksync-ethers.

Prerequisites

Fund your wallet

Follow the following guides to get PlayChain testnet ETH in your wallet:

You can check the balance of your account in the Albireo Explorer

Create the project

Run the following command in your terminal to create a new project using zkSync CLI.

npx zksync-cli create hello-playfi

It will give you options for different types of projects but for this tutorial choose the the following:

? What type of project do you want to create? Contracts
? Template: Hardhat + Solidity
? Private key of the wallet responsible for deploying contracts (optional) ***************************************************
? Package manager: yarn

Info

The private key of your wallet will be included in the .env file of the project and won't be pushed to GitHub.

The project structure is pretty straight forward:

  • hardhat.config.ts contains the general configuration for Hardhat and the zkSync plugins, which are already imported and setup.

  • /contracts contains smart contracts. zksync-cli provides common examples like an ERC20, an NFT, and the Greeter contract that we'll use later on.

  • /deploy contains the deployment scripts.

Add a new network entry in the hardhat.config.ts file:

playfiAlbireoTestnet: {
      url: "https://albireo-rpc.playfi.ai",
      ethNetwork: "sepolia",
      zksync: true,
      verifyURL: "https://albireo-verifier.playfi.ai/contract_verification",
    }

Set the defaultNetwork to this network:

defaultNetwork: "playfiAlbireoTestnet",

For this tutorial we'll focus on the /contracts/Greeter.sol contract:

//SPDX-License-Identifier: Unlicense
pragma solidity ^0.8.0;

contract Greeter {
    string private greeting;

    constructor(string memory _greeting) {
        greeting = _greeting;
    }

    function greet() public view returns (string memory) {
        return greeting;
    }

    function setGreeting(string memory _greeting) public {
        greeting = _greeting;
    }
}

As you can see, it a simple Solidity contract with two methods to read a message, greet(), and modify it, setGreeting().

Takeaway

PlayFi is EVM compatible. You can write smart contracts with Solidity or Vyper and use existing popular libraries like OpenZeppelin.

Compile the contract

Smart contracts deployed to PlayFi must be compiled using our custom compilers:

  • zksolc for Solidity contracts.

  • zkvyper for Vyper contracts.

As this is a Solidity project, it already has the hardhat-zksync-solc plugin installed and configured so there's nothing you need to setup. To compile the contracts in the project, run the following command:

yarn compile

You'll get the following output:

Compiling contracts for zkSync Era with zksolc v1.3.21 and solc v0.8.17
Compiling 46 Solidity files
Successfully compiled 46 Solidity files
✨  Done in 21.55s.

The compiled artifacts will be located in the /artifacts-zk folder. These artifacts are similar to the ones generated by the Solidity compiler. For example, the ABI of the Greeter contract will be located in /artifacts-zk/contracts/Greeter.sol/Greeter.json.

Takeaway

Smart contracts deployed to PlayFi must be compiled using zksolc or zkvyper as they generate a custom bytecode compatible with PlayFi's ZKEVM.

The configuration for the zksolc compiler is located in the zksolc section of the hardhat.config.ts file. You can find more info about the compiler settings in the hardhat-zksync-solc plugin and the compiler section of the ZK Stack documentation.

Deploy and verify

The project also contains a script to deploy and verify the contract in /deploy/deploy.ts. Under the hood, this script uses hardhat-zksync-deploy and hardhat-zksync-verify for deployment and contract verification.

import { deployContract } from "./utils";

// An example of a basic deploy script
// It will deploy a Greeter contract to selected network
// as well as verify it on Block Explorer if possible for the network
export default async function () {
  const contractArtifactName = "Greeter";
  const constructorArguments = ["Hi there!"];
  await deployContract(contractArtifactName, constructorArguments);
}

To execute it, just run:

yarn deploy

You'll get the following output:

Starting deployment process of "Greeter"...
Estimated deployment cost: 0.0000648863 ETH

"Greeter" was successfully deployed:
 - Contract address: 0x0BaF96A7f137B05d0D35b76d59B16c86C1791D8D
 - Contract source: contracts/Greeter.sol:Greeter
 - Encoded constructor arguments: 0x000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000094869207468657265210000000000000000000000000000000000000000000000

Requesting contract verification...
Your verification ID is: 1781

🥳 Congratulations! You just deployed a smart contract to PlayFi Albireo testnet. You can find it in the PlayFi Albireo explorer by searching the contract address.

In addition, the deployment script verified the contract automatically so you can see the source code in the contract tab of the block explorer.

Interact with the contract

The project also comes with a script to interact with the contract in /deploy/interact.ts. Add the address of the Greeter contract you just deployed in the CONTRACT_ADDRESS variable inside the /deploy/interact.ts file:

import * as hre from "hardhat";
import { getWallet } from "./utils";
import { ethers } from "ethers";

// Address of the contract to interact with
const CONTRACT_ADDRESS = "";
if (!CONTRACT_ADDRESS) throw "⛔️ Provide address of the contract to interact with!";

// An example of a script to interact with the contract
export default async function () {
  console.log(`Running script to interact with contract ${CONTRACT_ADDRESS}`);

  // Load compiled contract info
  const contractArtifact = await hre.artifacts.readArtifact("Greeter");

  // Initialize contract instance for interaction
  const contract = new ethers.Contract(
    CONTRACT_ADDRESS,
    contractArtifact.abi,
    getWallet() // Interact with the contract on behalf of this wallet
  );

  // Run contract read function
  const response = await contract.greet();
  console.log(`Current message is: ${response}`);

  // Run contract write function
  const transaction = await contract.setGreeting("Hello people!");
  console.log(`Transaction hash of setting new message: ${transaction.hash}`);

  // Wait until transaction is processed
  await transaction.wait();

  // Read message after transaction
  console.log(`The message now is: ${await contract.greet()}`);
}

As you can see, we're simply using ethers to interact with our contract. PlayFi is EVM compatible so you can use existing tools and libraries like Hardhat, ethers, web3.js, and users can use their existing wallets like Metamask, Rabby or Zerion.

Takeaway

Existing libraries like ethers and web3.js can be used to interact with smart contracts deployed on zkSync.

To execute the /deploy/interact.ts script, run:

yarn interact

You'll get the following output:

Running script to interact with contract 0x0BaF96A7f137B05d0D35b76d59B16c86C1791D8D
Current message is: Hi there!
Transaction hash of setting new message: 0x7a534857cfcd6df7e3eaf40a79a2c88f2e36bb60ce6f2399345e5431362b04eb
The message now is: Hello people!
✨  Done in 4.13s.

Congratulations! You've retrieved and updated the message on the Greeter contract. You can see the transaction in the PlayFi Albireo explorer by searching the transaction hash.

Takeaways

  • PlayFi is built on the ZKStack and is therefore EVM compatible. This means you can write smart contracts in Solidity or Vyper, use Hardhat, libraries like Ethers and Web3.js, or wallets like Metamask and Rabby.

  • zkSync CLI provides a quick way to scaffold different types of projects thanks to its multiple templates.

  • Contracts deployed to PlayFi are compiled using zksolc or zkvyper as they generate a special bytecode for PlayFi's ZKEVM.

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