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CONTRACT_2.md

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Web3 course
F.Borowiec
2022-01-12
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Counter contract

Let's create another contract responsible for incrementing a number.

Counter.sol:

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

import "hardhat/console.sol";  // console out from the contract

contract Counter {
    uint counter;

    function count () public returns (uint) {
        counter++;
        console.log("Counter is now: ", counter);
        return counter;
    }
}

And the deployment script deploy-counter.ts:

import "@nomiclabs/hardhat-ethers";
import { ethers } from "hardhat";

async function deploy() {
    const Counter = await ethers.getContractFactory("Counter");
    const counter = await Counter.deploy(); // builds a json request
    await counter.deployed();

    return counter;
}

// @ts-ignore
async function count(counter) {
    const message = await counter.count();
    console.log(message);
}

deploy().then(count);

Deployment

Let's npx hardhat compile and npx hardhat run scripts/deploy-counter.ts --network localhost.

Output (this is a transaction because we changed the contract):

{
  hash: '0xe63ace5363c8c0c474327d5ba7a9885790bf59ba408bd3034028a319401bba0c',
  type: 2,
  accessList: [],
  blockHash: '0xd18e2b56bc99e297e91c2036404678e5d219caaed710b3fe4e2d78011334cc8b',
  blockNumber: 3,
  transactionIndex: 0,
  confirmations: 1,
  from: '0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266',
  gasPrice: BigNumber { value: "672222034" },
  maxPriorityFeePerGas: BigNumber { value: "0" },
  maxFeePerGas: BigNumber { value: "850781011" },
  gasLimit: BigNumber { value: "47352" },
  to: '0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512',
  value: BigNumber { value: "0" },
  nonce: 2,
  data: '0x06661abd',
  r: '0x74d2fad79f245be55916556956737a1b6cfd4f4ad659ac21a364212c78eb2713',
  s: '0x29a0bc886559db5f2d4a5a7b19a96afde166238d99fa57acfd2c89d5a38627b9',
  v: 0,
  creates: null,
  chainId: 31337,
  wait: [Function (anonymous)]
}

Check also the output of the network:

hardhat_addCompilationResult
web3_clientVersion
eth_chainId
eth_accounts
eth_blockNumber
eth_chainId (2)
eth_estimateGas
eth_getBlockByNumber
eth_feeHistory
eth_sendTransaction
  Contract deployment: Counter
  Contract address:    0xe7f1725e7734ce288f8367e1bb143e90bb3f0512
  Transaction:         0x1d4cb0adfea46f403e9e90126a3bbc331509f44cc5c22ec6452a92f6965ff306
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  Value:               0 ETH
  Gas used:            225158 of 225158
  Block #2:            0xa93c0412ef1e2c85ae6b70b31dab719a7683f93f1ca2d64823909246695f9956

eth_chainId
eth_getTransactionByHash
eth_chainId
eth_getTransactionReceipt
eth_chainId
eth_estimateGas
eth_feeHistory
eth_sendTransaction
  Contract call:       Counter#count
  Transaction:         0xe63ace5363c8c0c474327d5ba7a9885790bf59ba408bd3034028a319401bba0c
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512
  Value:               0 ETH
  Gas used:            47352 of 47352
  Block #3:            0xd18e2b56bc99e297e91c2036404678e5d219caaed710b3fe4e2d78011334cc8b

  console.log:
    Counter is now:  1

eth_chainId
eth_getTransactionByHash

Storage is expensive - altered state means transactions take time to process.

Let's change the contract into two functions (one that does the mutation and the other that does the reading (for free)

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

import "hardhat/console.sol";  // console out from the contract

contract Counter {
    uint counter;

    function count () public {
        counter++;
        console.log("Counter is now: ", counter);
    }

    function getCounter() public view returns (uint) {
        return counter;
    }
}

Let's adapt the deployment script

import "@nomiclabs/hardhat-ethers";
import { ethers } from "hardhat";

async function deploy() {
    const Counter = await ethers.getContractFactory("Counter");
    const counter = await Counter.deploy(); // builds a json request
    await counter.deployed();

    return counter;
}

// @ts-ignore
async function count(counter) {
    await counter.count();
    const message = await counter.getCounter();
    console.log("Counter", message);
}

deploy().then(count);

After deploying it once again the output should be: Counter BigNumber: { value: "1" }

Note: BigNumber because javascript can't display solidity's uint256.

You can avoid that by casting to a uint32 inside the contract (be careful with overflows).

Environment variables

Go back to the contract and remove the hardcoded wallet value and change it to process.env.CONTRACT_ADDRESS that you will specify in a .env file inside your root.

The contract address is the last To address of the counter contract.

Let's also modify inside the index.ts the functions list to add the counter's contract functions.

import { ethers } from "ethers";

function getEth() {
    // @ts-ignore
    const eth = window.ethereum;
    if (!eth) {
        throw new Error("No Ethereum provider found");
    }
    return eth;
}

async function hasAccounts() {
    const eth = getEth();
    const accounts = await eth.request({ method: "eth_accounts" }) as string[];

    return accounts && accounts.length > 0 ? accounts : null;
}

async function requestAccounts() {
    const eth = getEth();
    const accounts = await eth.request({ method: "eth_requestAccounts" }) as string[];

    return accounts && accounts.length > 0 ? accounts : null;
}

async function run() {
    if (!await hasAccounts() && !await requestAccounts()) {
        throw new Error("No accounts found");
    }

    const counter = new ethers.Contract(
        process.env.CONTRACT_ADDRESS,
        [
            "function count() public",
            "function getCounter() public view returns (uint32)",
        ],
        new ethers.providers.Web3Provider(getEth()),
    )

    const el = document.createElement("div");
    async function setCounter() {
        el.innerHTML = await counter.getCounter();
    }
    setCounter();

    const button = document.createElement("button");
    button.innerText = "increment";
    button.onclick = async function() {
        setCounter();
    }

    document.body.appendChild(el);
    document.body.appendChild(button);
}

run();

And rerun webpack before deploying. DEPLOYING WILL FAIL!

How to deploy

Several things need to happen:

  • Add a new network to hardhat.config.ts:
  networks : {
    hardhat : {
      chainId : 1337,
    }
  }
  • Have python running a server from the dist folder on port 6969
  • Restart the node
  • Redeploy using the deployment script
  • Take the new address of the To from the eth_call
  • Substitute it in the .env
  • Restart webpack
  • Go to localhost:6969
  • Connect to MetaMask with the test account / Reset your account
  • Increment the counter
  • Add the new address (Counter contract) - Notice same address as in .env
  • Pay for the transaction

How to deploy to a real network

  • Create a Rinkeby network: faucets.chain.link/rinkeby
  • Deploy the Rinkeby network on alchemyapi.
  • Add the new netowrk to hardhat.config.ts:
    rinkeby: {
        url: `https://eth-rinkeby.alchemyapi.io/v2/${process.env.ALCHEMY_API_KEY}`,
        accounts: [`${process.env.RINKEBY_KEY}`],
    }
  • Add a console log of the address in the deploy function of the deployment script(in order to know to the scripts/deploy-counter.ts:
    await counter.deployed();

    console.log("Counter address:", counter.address);

    return counter;
  • Deploy it using the network's name: npx hardhat run scripts/deploy-counter.ts --network rinkeby
  • Use the new address to subsittute it inside the .env.
  • Restart npx webpack
  • Change the network on MetaMask to the new Rinkeby network.