FIN 451 — ICE7: Truffle Greeter Starter

Goal. You will: (1) set up Truffle, (2) write Greeter.sol, (3) compile, (4) deploy (migrate) to a local blockchain, and (5) read the greeting via a script.

Works on Windows, macOS, Linux. If lab PCs block global installs, use the “no-global” commands below.

0) What is a “Terminal” and where do I open it?

Terminal = a text window where you type commands (like node -v, truffle init). Also called command line, shell, or console.

On Windows

Command Prompt (CMD): Win → type cmd → Enter.
PowerShell: Win → type PowerShell → Enter.
Windows Terminal: Win → type Windows Terminal → Enter.
Open terminal in a folder:
- In File Explorer, go to the folder, click the address bar, type cmd → Enter.
- Or Shift+Right-click inside the folder → “Open in Terminal”.

On macOS

Terminal: Cmd+Space → type Terminal → Enter.
From Finder in a folder: Right-click → New Terminal at Folder (enable in Settings → Keyboard → Keyboard Shortcuts → Services).

On Linux

Press Ctrl+Alt+T, or search “Terminal”.

Inside VS Code (any OS)

Open your project in VS Code → menu View ▸ Terminal (or Ctrl+`).
The terminal starts in the folder shown in VS Code’s Explorer.

Basic navigation you’ll use:

# show where you are
pwd            # macOS/Linux
cd             # Windows PowerShell (prints current path)

# list files
ls             # macOS/Linux
dir            # Windows

# go into your project
cd my_truffle_project

# go up one folder
cd ..

IMPORTANT: Before running commands like truffle init or truffle compile, make sure your terminal’s current folder is your project folder (e.g., .../my_truffle_project). If not, use cd to go there first.

🆕 First time? Folder preview after truffle init:

my_truffle_project/
  contracts/
    Migrations.sol
  migrations/
    1_initial_migration.js
  test/
  truffle-config.js

You will add: contracts/Greeter.sol, migrations/2_deploy_greeter.js, and create scripts/scripts_test.js.

1) Setup

Install Node.js (LTS or v22). Verify:
```
node -v
npm -v
```

Install Truffle:

npm install -g truffle

No global installs? Use:

npm i -D truffle
npx truffle version

Create project:

mkdir my_truffle_project
cd my_truffle_project
truffle init

FYI You do not need to edit truffle-config.js for local development; Truffle Develop provides sane defaults.

2) Contract & Migration (exact save locations)

contracts/Greeter.sol

📂 Where to save: my_truffle_project/contracts/Greeter.sol
Windows example: C:\Users\YourName\my_truffle_project\contracts\Greeter.sol

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

contract Greeter {
    string public greeting;

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

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

migrations/2_deploy_greeter.js

📂 Where to save: my_truffle_project/migrations/2_deploy_greeter.js
Windows example: C:\Users\YourName\my_truffle_project\migrations\2_deploy_greeter.js

const Greeter = artifacts.require("Greeter");

module.exports = function (deployer) {
  deployer.deploy(Greeter, "Hello, JU!"); // change greeting if you like
};

Make the scripts folder & interaction script

📂 Where to save: create the folder my_truffle_project/scripts (if it doesn't exist), then save scripts_test.js inside it.
Windows example: C:\Users\YourName\my_truffle_project\scripts\scripts_test.js

const Greeter = artifacts.require("Greeter");

module.exports = async function (callback) {
  try {
    const instance = await Greeter.deployed();
    console.log("Contract address:", instance.address);
    const greeting = await instance.greet();
    console.log("Greeting:", greeting);
  } catch (err) {
    console.error(err);
  }
  callback();
};

Compile (build ABIs/artifacts)

truffle compile

Compile vs. Migrate — when to run which?
• Compile: turn Solidity into JSON artifacts in build/contracts/. Run after you change Solidity.
• Migrate: deploy contracts using files in migrations/. Run to put contracts on the chain.
• Changed only the migration (e.g., constructor args)? migrate --reset is enough.
• Changed the contract code? Run compile then migrate --reset.

3) Start Local Blockchain & Deploy

Start Truffle Develop (spins up a local chain + console):

truffle develop

Inside the special prompt truffle(develop)>, type commands without the truffle prefix:

compile
migrate
test   # optional

Two-terminal option Keep truffle develop open; in another terminal you can run truffle migrate --network development. For beginners, staying inside the console is simpler.

4) Interact via Script

Run inside the Truffle console

At the truffle(develop)> prompt:

exec scripts/scripts_test.js

Run from a normal terminal (keep develop running)

truffle exec scripts/scripts_test.js --network development

5) Expected Output

Contract address: 0x...YOUR_DEPLOYED_ADDRESS
Greeting: Hello, JU!

6) Copy/Paste Tips (Windows & Truffle console)

CMD: Right-click to paste (or enable “QuickEdit Mode”: title bar → Properties → QuickEdit).
PowerShell: Ctrl+V pastes; Ctrl+C may interrupt; use right-click or Ctrl+Shift+V.
Truffle console is still your terminal; paste works the same. If flaky, try Windows Terminal or run from a second terminal with truffle <cmd>.

7) Troubleshooting

Node/npm missing: Install Node. Check with node -v, npm -v.
“Could not connect to your Ethereum client”: Start truffle develop first, or use --network development.

Global installs blocked (lab PCs):

npm i -D truffle
npx truffle init
npx truffle develop

Port conflict / firewall:
```
truffle develop --port 8545
```
(Optional: add a matching development entry in truffle-config.js.)
Reset bad deployment:
```
migrate --reset
```
Changed Solidity? Rebuild then redeploy:
```
compile
migrate --reset
```

8) What next? Turn this into a tiny dapp (frontend)

Now that you can deploy and read the greeting in Node, let’s make a one-page web dapp that reads from the deployed contract.

Find your ABI JSON & address (after compiling & migrating):
- ABI file: my_truffle_project/build/contracts/Greeter.json (this is a big JSON with ABI + networks).
- Deployed address: shown after migrate and also inside that JSON under networks → (network id like 5777) → address.
Create a simple frontend (put this index.html next to your project or in a new folder):

📂 Where to save (simplest): Create a new folder like my_dapp, save the file below as index.html inside it.

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1" />
  <title>Greeter Dapp</title>
</head>
<body style="font-family:system-ui;padding:20px">
  <h1>Greeter Dapp</h1>
  <button id="connect">Connect MetaMask</button>
  <div id="out" style="margin-top:12px"></div>

  <script src="https://cdn.jsdelivr.net/npm/ethers@6.13.2/dist/ethers.umd.min.js"></script>
  <script>
    // 1) Paste ABI from build/contracts/Greeter.json (only the "abi" array)
    const ABI = [
      {"inputs":[{"internalType":"string","name":"_greeting","type":"string"}],"stateMutability":"nonpayable","type":"constructor"},
      {"inputs":[],"name":"greet","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},
      {"inputs":[],"name":"greeting","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"}
    ];
    // 2) Set ADDRESS to your deployed contract address printed by migrate
    const ADDRESS = "PASTE_YOUR_DEPLOYED_ADDRESS_HERE";

    const out = (msg) => document.getElementById('out').innerText = msg;

    document.getElementById('connect').onclick = async () => {
      if (!window.ethereum) { out('Install MetaMask first.'); return; }
      // Request accounts and connect to the browser provider (MetaMask)
      await window.ethereum.request({ method: 'eth_requestAccounts' });
      const provider = new ethers.BrowserProvider(window.ethereum);
      // 3) Ensure MetaMask is on the same network as your contract (Truffle Develop is usually 5777)
      const net = await provider.getNetwork();
      console.log('Connected network:', net);
      // 4) Read greeting
      const contract = new ethers.Contract(ADDRESS, ABI, provider);
      const g = await contract.greet();
      out('Greeting: ' + g);
    };
  </script>
</body>
</html>

Very important: If you re-deploy the contract, the address changes. Update ADDRESS in your frontend. If you change the Solidity interface, re-copy the ABI from Greeter.json.

Prefer React/Vite later?

# from a parent folder
npm create vite@latest my-react-dapp -- --template react
cd my-react-dapp
npm i
npm i ethers
npm run dev

Then put ABI + address in a config and call via ethers.BrowserProvider similarly.

9) Later: replacing files for new assignments

Replace Solidity: put your new contract in contracts/. Then:
```
compile
migrate --reset
```
Replace migration: update migrations/2_deploy_*.js (constructor args, contract name). Then:
```
migrate --reset
```

Replace the script: edit scripts/scripts_test.js for new function names. Then:

exec scripts/scripts_test.js   # inside develop console
# or
truffle exec scripts/scripts_test.js --network development

Frontend JSON (“the ABI file”): after compile, re-copy ABI from build/contracts/<YourContract>.json and update the deployed address in your frontend.

Remember: Changing contract code ⇒ new ABI and usually a new address. Your UI must be updated with both.

Submission: Zip your project (omit node_modules) or push to a repo. Include screenshot(s) showing the contract address and greeting.