How to Write Smart Contracts on Ethereum: A Developer’s Guide

How to Write Smart Contracts on Ethereum: A Developer’s Guide

Ethereum


Introduction to Ethereum Smart Contracts

Smart contracts are self-executing programs stored on the Ethereum blockchain. They automate agreements without intermediaries, enabling:
✅ Decentralized apps (DApps)
✅ Token creation (ERC-20, ERC-721)
✅ Automated financial transactions (DeFi)

Key Properties:

  • Immutable – Once deployed, code cannot be changed
  • Transparent – Anyone can verify contract logic
  • Trustless – Runs exactly as programmed

Prerequisites for Writing Smart Contracts

1. Basic Programming Knowledge

  • Familiarity with JavaScript or Python helps
  • Understanding of object-oriented programming (OOP)

2. Essential Tools

ToolPurpose
MetaMaskEthereum wallet for testing
Remix IDEBrowser-based Solidity editor
HardhatLocal Ethereum development environment
Alchemy/InfuraBlockchain node providers
Ethereum


Step-by-Step Guide to Writing Your First Smart Contract

Step 1: Set Up Your Development Environment

  1. Install Node.js (v16+)
  2. Install Hardhat (for local testing):
   npm install --save-dev hardhat
   npx hardhat init
  1. Connect MetaMask to a testnet (Goerli or Sepolia)

Step 2: Write a Simple Smart Contract in Solidity

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

contract SimpleStorage {
    uint storedData;

    function set(uint x) public {
        storedData = x;
    }

    function get() public view returns (uint) {
        return storedData;
    }
}

Explanation:

  • pragma solidity ^0.8.0 → Specifies Solidity version
  • contract SimpleStorage → Defines the contract
  • set() and get() → Functions to store/retrieve data

Step 3: Compile and Deploy

  1. In Remix:
  • Paste code → Compile (Ctrl+S) → Deploy
  1. In Hardhat:
   npx hardhat compile
   npx hardhat run scripts/deploy.js --network goerli

Best Practices for Secure Smart Contracts

1. Avoid Common Vulnerabilities

RiskSolution
Reentrancy attacksUse nonReentrant modifier
Overflows/UnderflowsUse OpenZeppelin’s SafeMath
Unchecked external callsValidate inputs with require()

2. Use OpenZeppelin Libraries

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";

contract MyToken is ERC20 {
    constructor() ERC20("MyToken", "MTK") {
        _mint(msg.sender, 1000000 * 10**18);
    }
}

📌 OpenZeppelin Contracts

3. Test Thoroughly Before Deployment

  • Write unit tests with Hardhat + Chai
  • Use Slither for static analysis:
  pip install slither-analyzer
  slither .

Deploying to Mainnet vs. Testnets

NetworkUse CaseCost
Ethereum MainnetProduction appsHigh (gas fees)
Goerli/SepoliaTestingFree (faucets available)
Polygon MumbaiLow-cost testingMinimal fees

📌 Get test ETH from Goerli Faucet

Next Steps: Advanced Smart Contract Development

  1. Learn Gas Optimization
  • Reduce storage writes
  • Use view/pure functions
  1. Explore DeFi Protocols
  • Study Uniswap, Aave, Compound
  1. Audit Smart Contracts

Conclusion

Writing Ethereum smart contracts requires:
🔹 Solidity knowledge
🔹 Proper tooling (Remix, Hardhat, MetaMask)
🔹 Security best practices

Start with small contracts, test rigorously, and gradually build complex DApps!

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