Smart Contract Standards

Introduction

Smart contract standards ensure interoperability and compatibility across the Ethereum ecosystem. This guide covers essential standards, their implementations, and best practices.

Token Standards

ERC20 Standard

The fundamental standard for fungible tokens:

interface IERC20 {
    function totalSupply() external view returns (uint256);
    function balanceOf(address account) external view returns (uint256);
    function transfer(address to, uint256 amount) external returns (bool);
    function allowance(address owner, address spender) external view returns (uint256);
    function approve(address spender, uint256 amount) external returns (bool);
    function transferFrom(address from, address to, uint256 amount) external returns (bool);
    
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

Key features:

• Fungible token operations
• Allowance mechanism
• Standard events
• Wide compatibility

ERC721 Standard

The standard for non-fungible tokens (NFTs):

interface IERC721 {
    function balanceOf(address owner) external view returns (uint256);
    function ownerOf(uint256 tokenId) external view returns (address);
    function safeTransferFrom(address from, address to, uint256 tokenId) external;
    function transferFrom(address from, address to, uint256 tokenId) external;
    function approve(address to, uint256 tokenId) external;
    function getApproved(uint256 tokenId) external view returns (address);
    function setApprovalForAll(address operator, bool approved) external;
    function isApprovedForAll(address owner, address operator) external view returns (bool);
}

Extensions:

• Metadata (ERC721Metadata)
• Enumerable (ERC721Enumerable)
• URIStorage
• Royalty support (ERC2981)

ERC1155 Standard

Multi-token standard for both fungible and non-fungible tokens:

interface IERC1155 {
    function balanceOf(address account, uint256 id) external view returns (uint256);
    function balanceOfBatch(address[] calldata accounts, uint256[] calldata ids) 
        external view returns (uint256[] memory);
    function setApprovalForAll(address operator, bool approved) external;
    function isApprovedForAll(address account, address operator) external view returns (bool);
    function safeTransferFrom(address from, address to, uint256 id, uint256 amount, bytes calldata data) 
        external;
    function safeBatchTransferFrom(address from, address to, uint256[] calldata ids, 
        uint256[] calldata amounts, bytes calldata data) external;
}

Features:

• Batch operations
• Mixed token types
• Gas efficiency
• URI management

Security Standards

Access Control

• Role-based access control (RBAC)
• Owner privileges
• Multi-signature systems
• Time locks

Implementation example:

contract AccessControl {
    mapping(bytes32 => mapping(address => bool)) private _roles;
    
    event RoleGranted(bytes32 indexed role, address indexed account);
    event RoleRevoked(bytes32 indexed role, address indexed account);
    
    modifier onlyRole(bytes32 role) {
        require(hasRole(role, msg.sender), "AccessControl: unauthorized");
        _;
    }
    
    function hasRole(bytes32 role, address account) public view returns (bool) {
        return _roles[role][account];
    }
}

Safety Checks

• Reentrancy protection
• Integer overflow/underflow
• Front-running prevention
• Oracle manipulation

Example pattern:

contract ReentrancyGuard {
    bool private locked;
    
    modifier nonReentrant() {
        require(!locked, "ReentrancyGuard: reentrant call");
        locked = true;
        _;
        locked = false;
    }
}

Development Standards

Code Quality

• Follow style guide
• Document thoroughly
• Test comprehensively
• Use verified libraries

Gas Optimization

• Pack storage variables
• Batch operations
• Cache storage reads
• Minimize state changes

Contract Interaction

• Safe external calls
• Event logging
• Error handling
• Proxy patterns

Best Practices

1. Security First

   • Use latest compiler
   • Follow audited patterns
   • Implement safeguards
   • Handle edge cases

2. Gas Efficiency

   • Optimize storage
   • Minimize operations
   • Use events wisely
   • Batch when possible

3. Maintainability

   • Clear documentation
   • Modular design
   • Upgrade strategy
   • Version control

Implementation Guide

Each standard requires:

1. Interface compliance
2. Security measures
3. Gas optimization
4. Thorough testing

Remember: Always prioritize security and follow established patterns when implementing these standards!