Smart Contracts

smart-contracts

Purpose

This skill focuses on developing, compiling, deploying, and interacting with secure smart contracts using Solidity for writing code and Web3.js for blockchain interactions, targeting platforms like Ethereum.

When to Use

Use this skill for tasks involving decentralized applications (dApps), token creation, or automated agreements on EVM-compatible blockchains. Apply it when you need to ensure code security, handle transactions, or integrate with Web3 ecosystems, such as building NFTs or DeFi protocols.

Key Capabilities

• Write and compile Solidity contracts with features like inheritance, modifiers, and events.
• Deploy contracts to testnets (e.g., Sepolia) or mainnets using Web3.js providers.
• Interact with deployed contracts via RPC calls, including reading state and executing functions.
• Perform security audits by integrating tools like Slither for vulnerability detection.
• Handle Web3 transactions with gas estimation and error checking.

Usage Patterns

To use this skill, structure your workflow as follows: First, write Solidity code in a .sol file. Then, compile it using a tool like Hardhat or solc. Deploy via a Web3 provider, and interact using JavaScript. Always test on a local node (e.g., Ganache) before mainnet. For integration, pass provider URLs as environment variables, like $ETHEREUM_PROVIDER_URL. Example pattern: Import Web3.js, connect to a provider, and call contract methods in a Node.js script.

Common Commands/API

Use solc for compilation: solc --optimize --bin input.sol -o build/. For deployment with Hardhat, run npx hardhat run scripts/deploy.js --network sepolia. Web3.js API: Create a provider with const web3 = new Web3($ETHEREUM_PROVIDER_URL); and call web3.eth.getBalance(address). For contract interaction, use ABI: contract.methods.myFunction().send({from: account, gas: 200000}). Config format: In Hardhat.config.js, define networks like networks: { sepolia: { url: process.env.SEPOLIA_URL, accounts: [process.env.PRIVATE_KEY] } }, where $SEPOLIA_URL and $PRIVATE_KEY are env vars. Authenticate with Infura by setting $INFURA_API_KEY in the provider URL.

Integration Notes

Integrate this skill by installing dependencies like npm install hardhat web3. Set up a .env file for sensitive data (e.g., ETHEREUM_PRIVATE_KEY=$YOUR_PRIVATE_KEY). For external APIs, use providers like Infura or Alchemy with URLs formatted as https://mainnet.infura.io/v3/$INFURA_API_KEY. Ensure compatibility by using Web3.js version 1.x for Etherscan verification. To link with other skills, export contract ABIs as JSON for downstream use, e.g., in a frontend with React.

Error Handling

Handle compilation errors by checking solc output for messages like "ParserError: Expected token". For deployment, catch Web3.js errors with try-catch blocks, e.g., try { await contract.deploy({data: bytecode}); } catch (e) { if (e.message.includes('gas')) console.error('Insufficient gas'); }. Common issues: Reverted transactions (check with web3.eth.getTransactionReceipt(txHash) for status); use events for asynchronous error logging. For security, validate inputs in Solidity with require statements, e.g., require(msg.sender == owner, "Not authorized");. Always use a funded account and monitor gas limits.

Concrete Usage Examples

1. Write and Deploy a Simple Storage Contract: Create a file SimpleStorage.sol with pragma solidity ^0.8.0; contract SimpleStorage { uint storedData; function set(uint x) public { storedData = x; } }. Compile with solc --bin SimpleStorage.sol. Deploy using Hardhat: In deploy.js, write const SimpleStorage = await ethers.getContractFactory("SimpleStorage"); const contract = await SimpleStorage.deploy(); await contract.deployed();. Run npx hardhat run deploy.js --network localhost. 2. Interact with an ERC20 Token Contract: Assume a deployed token at address 0xTokenAddress. In a Node.js script: const web3 = new Web3($ETHEREUM_PROVIDER_URL); const contract = new web3.eth.Contract(ABI, '0xTokenAddress'); await contract.methods.transfer('0xRecipient', 100).send({from: '0xYourAddress', gas: 50000});. Handle with error checking for insufficient funds.

Graph Relationships

• Related to cluster: "blockchain" (e.g., shares tools with other blockchain skills).
• Connected via tags: "solidity" (links to language-specific tools), "smart-contracts" (cross-references deployment patterns), "blockchain" (integrates with general blockchain APIs).
• Outgoing edges: To "web3" for provider interactions, to "ethereum" for network specifics.