Discussion on: The Complete Guide to Full Stack Ethereum and EVM Development

[Horace Nelson]

Here's the deploy output:

Starting: scripts/deploy.js --network localhost
Deploying contracts with the account: 0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266
Deploying a Greeter with greeting: Hello, World!
Greeter deployed to: 0x5FbDB2315678afecb367f032d93F642f64180aa3
Token deployed to: 0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512

And here's my App.js:

import './App.css';
import { useState } from 'react';
import { ethers } from 'ethers'
import Greeter from './artifacts/contracts/Greeter.sol/Greeter.json'
import Token from './artifacts/contracts/Token.sol/Token.json'
const greeterAddress = "0x5FbDB2315678afecb367f032d93F642f64180aa3"
const tokenAddress = "0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512"

function App() {
  const [greeting, setGreetingValue] = useState()
  const [userAccount, setUserAccount] = useState()
  const [amount, setAmount] = useState()

  async function requestAccount() {
    await window.ethereum.request({ method: 'eth_requestAccounts' });
  }

  async function fetchGreeting() {
    if (typeof window.ethereum !== 'undefined') {
      const provider = new ethers.providers.Web3Provider(window.ethereum)
      console.log({ provider })
      const contract = new ethers.Contract(greeterAddress, Greeter.abi, provider)
      try {
        const data = await contract.greet()
        console.log('data: ', data)
      } catch (err) {
        console.log("Error: ", err)
      }
    }    
  }

  async function getBalance() {
    if (typeof window.ethereum !== 'undefined') {
      const [account] = await window.ethereum.request({ method: 'eth_requestAccounts' })
      console.log({ account }) // outputs { account: "0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266" }
      const provider = new ethers.providers.Web3Provider(window.ethereum);
      const signer = provider.getSigner()
      const contract = new ethers.Contract(tokenAddress, Token.abi, signer)

      // THIS THROWS
      contract.balanceOf(account)
        .then(data => {
          console.log("data: ", data.toString())
        })
    }
  }

  async function setGreeting() {
    if (!greeting) return
    if (typeof window.ethereum !== 'undefined') {
      await requestAccount()
      const provider = new ethers.providers.Web3Provider(window.ethereum);
      console.log({ provider })
      const signer = provider.getSigner()
      const contract = new ethers.Contract(greeterAddress, Greeter.abi, signer)
      const transaction = await contract.setGreeting(greeting)
      await transaction.wait()
      fetchGreeting()
    }
  }

  async function sendCoins() {
    if (typeof window.ethereum !== 'undefined') {
      await requestAccount()
      const provider = new ethers.providers.Web3Provider(window.ethereum);
      const signer = provider.getSigner()
      const contract = new ethers.Contract(tokenAddress, Token.abi, signer)
      contract.transfer(userAccount, amount).then(data => console.log({ data }))
    }
  }

  return (
    <div className="App">
      <header className="App-header">
        <button onClick={fetchGreeting}>Fetch Greeting</button>
        <button onClick={setGreeting}>Set Greeting</button>
        <input onChange={e => setGreetingValue(e.target.value)} placeholder="Set greeting" />

        <br />
        <button onClick={getBalance}>Get Balance</button>
        <button onClick={sendCoins}>Send Coins</button>
        <input onChange={e => setUserAccount(e.target.value)} placeholder="Account ID" />
        <input onChange={e => setAmount(e.target.value)} placeholder="Amount" />
      </header>
    </div>
  );
}

export default App;

[Simranjeet Singh]

const provider = new ethers.providers.Web3Provider(window.ethereum);
const signer = provider.getSigner(); // remove this
const contract = new ethers.Contract(tokenAddress, Token.abi, signer); // replace signer with provider

signing is not required here!

[Jamiebones]

Signing is required.

[Nader Dabit]

Hey, not sure why you would run into that, did you figure it out?

[Dominic Wong]

I am running into the same issue

[Dominic Wong]

It worked when I called balanceOf inside deploy.js, just not when calling from App.js

[Nikolay]

Stuck with the same issue. After some deep dive into hardhat docs finally, I've found the cause.
It looks like instead

npx run scripts/deploy.js --network localhost

should be

npx run hardhat scripts/deploy.js --network localhost

@dabit3 could you please correct it?

[Himika Prabhat]

It still ain't working for me, even after making this change

[Dav]

I faced the same issue too and figured it out. First, make sure you've selected the right MetaMask network. If you deployed to a local node, make sure the selected MetaMask network on your browser is Localhost: 8545. If you deployed to ropsten, make sure you've selected Ropsten Test Network. Secondly, each time you successfully deploy your contract, make sure you correctly copy and reference the generated contract address if you intend to interact with the newly deployed contract without errors. Just like @richardmelko advised, make sure that your tokenAddress is pointing the Token contract address you copied after deployment.