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OpenZeppelin Smart Contracts Guide

This document provides an organized and comprehensive guide to OpenZeppelin smart contracts, covering their use cases, import statements, and implementation scenarios. Follow this to choose the right contract for your specific use case, optimize for gas, and ensure security.

Table of Contents

Access Control Contracts

1. AccessControl.sol

Use Cases:

  • Role-based access control for multiple roles
  • Complex permission systems (e.g., admin, moderator, user)
  • Need different admin roles for various functions

Import Statement:

import "@openzeppelin/contracts/access/AccessControl.sol";

Additional Content: Use grantRole, revokeRole, and hasRole to manage permissions.

2. Ownable.sol

Use Cases:

  • Simple single-owner access control
  • Transferable ownership
  • Basic admin functionality

Import Statement:

import "@openzeppelin/contracts/access/Ownable.sol";

Additional Content: Provides transferOwnership and onlyOwner modifiers.

3. IAccessControl.sol

Use Cases:

  • Custom access control systems
  • Create interfaces to interact with AccessControl
  • Build role-based systems from scratch

Import Statement:

import "@openzeppelin/contracts/access/IAccessControl.sol";

Token Contracts

ERC20 Contracts

1. ERC20.sol

Use Cases:

  • Basic fungible token creation
  • Need standard token functionality (e.g., transfer, approve)

Import Statement:

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

2. ERC20Burnable.sol

Use Cases:

  • Enable token burning
  • Deflationary token mechanisms

Import Statement:

import "@openzeppelin/contracts/token/ERC20/extensions/ERC20Burnable.sol";

3. ERC20Capped.sol

Use Cases:

  • Token with a maximum supply limit
  • Fixed supply tokens

Import Statement:

import "@openzeppelin/contracts/token/ERC20/extensions/ERC20Capped.sol";

4. ERC20Pausable.sol

Use Cases:

  • Add emergency stop functionality
  • Temporarily freeze transfers

Import Statement:

import "@openzeppelin/contracts/token/ERC20/extensions/ERC20Pausable.sol";

5. ERC20Snapshot.sol

Use Cases:

  • Maintain historical balances
  • Use in dividend distribution or voting systems

Import Statement:

import "@openzeppelin/contracts/token/ERC20/extensions/ERC20Snapshot.sol";

ERC721 Contracts

1. ERC721.sol

Use Cases:

  • Basic NFT functionality
  • Unique digital assets

Import Statement:

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";

2. ERC721Enumerable.sol

Use Cases:

  • Enumerate NFTs for marketplaces or stats
  • Need to track total supply and ownership

Import Statement:

import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Enumerable.sol";

3. ERC721URIStorage.sol

Use Cases:

  • Dynamic metadata for NFTs
  • Customizable token properties

Import Statement:

import "@openzeppelin/contracts/token/ERC721/extensions/ERC721URIStorage.sol";

ERC1155 Contracts

1. ERC1155.sol

Use Cases:

  • Multiple token types (fungible & non-fungible)
  • Gaming items or large collections

Import Statement:

import "@openzeppelin/contracts/token/ERC1155/ERC1155.sol";

Security Contracts

1. ReentrancyGuard.sol

Use Cases:

  • Prevent reentrancy attacks on functions
  • Safeguard token transfers and external calls

Import Statement:

import "@openzeppelin/contracts/security/ReentrancyGuard.sol";

2. Pausable.sol

Use Cases:

  • Add an emergency stop mechanism
  • Temporary halt critical operations

Import Statement:

import "@openzeppelin/contracts/security/Pausable.sol";

Utilities

1. SafeMath.sol

Use Cases:

  • Prevent overflow/underflow in versions <0.8.0

Import Statement:

import "@openzeppelin/contracts/utils/math/SafeMath.sol";

2. Counters.sol

Use Cases:

  • Token IDs or incremental counters

Import Statement:

import "@openzeppelin/contracts/utils/Counters.sol";

Governance Contracts

1. Governor.sol

Use Cases:

  • Implement decentralized voting systems
  • On-chain governance for DAOs

Import Statement:

import "@openzeppelin/contracts/governance/Governor.sol";

2. TimelockController.sol

Use Cases:

  • Time-lock administrative functions
  • Delayed governance actions for transparency

Import Statement:

import "@openzeppelin/contracts/governance/TimelockController.sol";

Proxy Contracts

1. ERC1967Proxy.sol

Use Cases:

  • Upgradeable smart contracts

Import Statement:

import "@openzeppelin/contracts/proxy/ERC1967/ERC1967Proxy.sol";

2. Clones.sol

Use Cases:

  • Minimal proxies for gas optimization
  • Factory patterns

Import Statement:

import "@openzeppelin/contracts/proxy/Clones.sol";

Common Implementations

DeFi Lending Platform

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@openzeppelin/contracts/security/Pausable.sol";
import "@openzeppelin/contracts/access/AccessControl.sol";

NFT Marketplace

import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Royalty.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

This guide serves as a quick reference for integrating OpenZeppelin contracts into your projects. For best practices, always use the latest versions, thoroughly test contracts, and review the official OpenZeppelin Documentation.