Get Started

# ===== 1. Tools =====
# Wallet:    MetaMask / Rabby (browser extensions)
# Library:   viem (TypeScript-first) or ethers.js
# Test chain: Anvil (Foundry) or Hardhat node
# Contracts: Solidity via Foundry (forge) or Hardhat

# ===== 2. Install Foundry =====
curl -L https://foundry.paradigm.xyz | bash
foundryup

forge --version
anvil --version

# ===== 3. New project =====
forge init my-app
cd my-app

# src/Counter.sol
# pragma solidity ^0.8.20;
# contract Counter {
#   uint256 public n;
#   function bump() public { n += 1; }
# }

forge build
forge test       # runs the demo tests

# ===== 4. Local chain =====
anvil &           # starts a local chain on http://127.0.0.1:8545
# anvil prints accounts + private keys; use one for testing.

# ===== 5. Deploy locally =====
forge script script/Counter.s.sol --rpc-url http://127.0.0.1:8545 --broadcast \
  --private-key 0xYOUR_TEST_KEY

# Or the simple way:
forge create src/Counter.sol:Counter --rpc-url http://127.0.0.1:8545 --private-key 0xYOUR_TEST_KEY

# Note the deployed address printed.

# ===== 6. Frontend with Vite + viem =====
npm create vite@latest dapp -- --template react-ts
cd dapp
npm install viem

# src/main.tsx
import { createPublicClient, createWalletClient, custom, http, getContract } from 'viem';
import { foundry } from 'viem/chains';

const ABI = [{ name: 'bump', type: 'function', stateMutability: 'nonpayable', inputs: [], outputs: [] },
             { name: 'n', type: 'function', stateMutability: 'view', inputs: [], outputs: [{ type: 'uint256' }] }];

const pub = createPublicClient({ chain: foundry, transport: http() });
const counter = getContract({ address: '0xDEPLOYED', abi: ABI, client: { public: pub } });

const n = await counter.read.n();
console.log('count', n);

# Write via wallet:
async function bumpFromWallet() {
  if (!window.ethereum) throw new Error('No wallet');
  const wallet = createWalletClient({ chain: foundry, transport: custom(window.ethereum) });
  const [address] = await wallet.requestAddresses();
  const hash = await wallet.writeContract({ address: '0xDEPLOYED', abi: ABI, functionName: 'bump', account: address });
  console.log('tx', hash);
}

# ===== 7. Connect MetaMask to Anvil =====
# In MetaMask: Networks -> Add a network
#   Name: Anvil
#   RPC: http://127.0.0.1:8545
#   Chain ID: 31337
# Import a private key from the anvil output.

# ===== 8. Move to a testnet =====
# Sepolia (ETH), Optimism Sepolia, Arbitrum Sepolia.
# Get test ETH from a faucet.
# Use --rpc-url <sepolia_rpc> to deploy; verify on Etherscan with --verify.

# forge create ... --rpc-url $SEPOLIA --private-key $KEY --verify --etherscan-api-key $ETHERSCAN_KEY

# ===== 9. Don't ship to mainnet on day one =====
# - Test thoroughly on a public testnet
# - Get an audit for any contract holding real funds
# - Add a pause function + admin timelock
# - Document the contract address + ABI

# ===== Patterns to internalise =====
# - Anvil + Foundry for local dev (fast, modern, well-documented)
# - viem + TypeScript at the frontend
# - Read via public client; write via wallet client
# - Pin chain + addresses in config; do not hardcode anywhere else

# ===== Pitfalls =====
# - Mainnet keys in local .env files
# - Sending real ETH to a Sepolia contract address (different chain)
# - Hardcoding addresses across environments
# - Trusting your own contract before audits + testnet time

# Foundry — fast, Rust-built toolchain
curl -L https://foundry.paradigm.xyz | bash
foundryup
forge init myproject && cd myproject
forge test