Hello World Smart Contract Tutorial for the Celo Blockchain

celo_deploy.js

const Web3 = require('web3')
const ContractKit = require('@celo/contractkit')
const web3 = new Web3('https://alfajores-forno.celo-testnet.org')
const kit = ContractKit.newKitFromWeb3(web3)
const getAccount = require('./getAccount').getAccount
const HelloWorld = require('./build/contracts/HelloWorld.json')

async function awaitWrapper(){
    let account = await getAccount()
    
    // This account must have a CELO balance to pay tx fees 
    // get some testnet funds at https://celo.org/build/faucet
    console.log(account.address)
    
    kit.connection.addAccount(account.privateKey) // this account must have a CELO balance to pay transaction fees

    let tx = await kit.connection.sendTransaction({
        from: account.address,
        data: HelloWorld.bytecode
    })

    const receipt = await tx.waitReceipt()
    console.log(receipt)
}

awaitWrapper()

helloWorld.js

// This script requires that you have already deployed HelloWorld.sol with Truffle
// Go back and do that if you haven't already

// Account address: 0x8d02CC83da06eF1BE14c2df6289ED9F8Af64fBAf

// 1. Import web3 and contractkit 
const Web3 = require("web3")
const ContractKit = require('@celo/contractkit')

// 2. Import the getAccount function
const getAccount = require('./getAccount').getAccount

// 3. Init a new kit, connected to the alfajores testnet
const web3 = new Web3('https://alfajores-forno.celo-testnet.org')
const kit = ContractKit.newKitFromWeb3(web3)

// import HelloWorld info
const HelloWorld = require('./build/contracts/HelloWorld.json')

// Initialize a new Contract interface
async function initContract(){
    // Check the Celo network ID
    const networkId = await web3.eth.net.getId();
    const deployedNetwork = HelloWorld.networks[networkId];
    // Create a new contract instance with the HelloWorld contract info
    let instance = new web3.eth.Contract(
        HelloWorld.abi,
        deployedNetwork && deployedNetwork.address
    );

    getName(instance)
    setName(instance, "hello world!")
}

// Read the 'name' stored in the HelloWorld.sol contract
async function getName(instance){
    let name = await instance.methods.getName().call()
    console.log(name)
}

// Set the 'name' stored in the HelloWorld.sol contract
async function setName(instance, newName){
    let account = await getAccount()

    // Add your account to ContractKit to sign transactions
    // This account must have a CELO balance to pay tx fees, get some https://celo.org/build/faucet
    kit.connection.addAccount(account.privateKey)
    
    // Encode the transaction to HelloWorld.sol according to the ABI
    let txObject = await instance.methods.setName(newName)
    
    // Send the transaction
    let tx = await kit.sendTransactionObject(txObject, { from: account.address })

    let receipt = await tx.waitReceipt()
    console.log(receipt)
}

initContract()

HelloWorld.sol

// SPDX-License-Identifier: MIT
pragma solidity >=0.4.22 <0.8.0;

contract HelloWorld {
  string name = "Celo";
  
  function getName() public view returns (string memory) {
    return name;
  }

  function setName(string memory input) public {
    name = input;
  }
}