Building a Complete NFT Launchpad: Part 1 - Smart Contracts

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Hey NFT enthusiasts! 👋 Ever wondered how platforms like OpenSea and Rarible allow creators to launch their NFT collections without spending a fortune on gas? In this first part of our NFT Launchpad series, we'll dive deep into creating a gas-optimized smart contract foundation for your platform.

What is an NFT Launchpad? 🚀

Think of an NFT Launchpad as a factory that creates and manages NFT collections. Instead of creators having to deploy their own smart contracts (which can be risky and expensive), they use your platform to launch their collections securely and cost-effectively.

Here's the architecture we'll build:

graph TD
    A[Launchpad Factory Contract] -->|Clones| B[Implementation Contract]
    B -->|Minimal Proxy| C[Collection 1]
    B -->|Minimal Proxy| D[Collection 2]
    B -->|Minimal Proxy| E[Collection 3]
    C -->|Mints| F[NFTs]
    D -->|Mints| G[NFTs]
    E -->|Mints| H[NFTs]
    style B fill:#f9f,stroke:#333,stroke-width:4px

Understanding the Imports 📚

Before we dive into the code, let's understand the key OpenZeppelin contracts we'll be using:

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@openzeppelin/contracts/proxy/Clones.sol";
import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/utils/Counters.sol";

Let's break down why we need each import:

1. Ownable.sol

   • Provides basic access control

   • Enables owner-only functions like fee withdrawal

   • Includes safe ownership transfer mechanisms

2. ReentrancyGuard.sol

   • Prevents reentrancy attacks

   • Essential for functions handling ETH transfers

   • Uses a simple mutex pattern

3. Clones.sol

   • Implements EIP-1167 minimal proxy pattern

   • Reduces deployment costs by ~95%

   • Enables cheap collection creation

4. ERC721.sol

   • Base implementation for NFT standard

   • Includes core NFT functions

   • Handles ownership and transfers

5. Counters.sol

   • Safe counter for token IDs

   • Prevents overflow errors

   • Simple increment/decrement operations

The Factory Contract 🏭

Let's implement our gas-optimized Factory Contract:

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

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@openzeppelin/contracts/proxy/Clones.sol";

contract NFTLaunchpadFactory is Ownable, ReentrancyGuard {
    using Clones for address;

    // Implementation contract address that will be cloned
    address public immutable implementationContract;

    // Fee structure
    uint256 public creationFee = 0.1 ether;
    uint256 public platformFeePercentage = 5; // 5% of mint price

    // Collection tracking
    struct Collection {
        address contractAddress;
        address creator;
        uint256 mintPrice;
        uint256 maxSupply;
        bool isActive;
    }

    mapping(address => Collection) public collections;
    address[] public allCollections;

    event CollectionCreated(
        address indexed collectionAddress,
        address indexed creator,
        uint256 mintPrice,
        uint256 maxSupply
    );

    constructor() {
        // Deploy the implementation contract once
        implementationContract = address(new NFTCollection());
    }

    // Create new collection using minimal proxy clone
    function createCollection(
        string memory name,
        string memory symbol,
        uint256 mintPrice,
        uint256 maxSupply
    ) external payable nonReentrant {
        require(msg.value >= creationFee, "Insufficient creation fee");

        // Clone the implementation contract
        address clone = implementationContract.clone();

        // Initialize the clone
        NFTCollection(clone).initialize(
            name,
            symbol,
            mintPrice,
            maxSupply,
            msg.sender,
            address(this)
        );

        // Store collection details
        collections[clone] = Collection({
            contractAddress: clone,
            creator: msg.sender,
            mintPrice: mintPrice,
            maxSupply: maxSupply,
            isActive: true
        });

        allCollections.push(clone);

        emit CollectionCreated(
            clone,
            msg.sender,
            mintPrice,
            maxSupply
        );
    }

    // Withdraw platform fees
    function withdrawFees() external onlyOwner {
        payable(owner()).transfer(address(this).balance);
    }
}

The NFT Collection Contract Template 🎨

Here's our optimized NFT Collection contract that will be cloned:

contract NFTCollection is ERC721, ReentrancyGuard {
    using Counters for Counters.Counter;

    Counters.Counter private _tokenIds;
    uint256 public mintPrice;
    uint256 public maxSupply;
    address public creator;
    address public launchpad;
    string public baseURI;

    bool private initialized;

    // Remove constructor and add initializer
    function initialize(
        string memory name,
        string memory symbol,
        uint256 _mintPrice,
        uint256 _maxSupply,
        address _creator,
        address _launchpad
    ) external {
        require(!initialized, "Already initialized");
        initialized = true;

        // Initialize ERC721
        _initialize(name, symbol);

        mintPrice = _mintPrice;
        maxSupply = _maxSupply;
        creator = _creator;
        launchpad = _launchpad;
    }

    function mint() external payable nonReentrant {
        require(initialized, "Not initialized");
        require(msg.value >= mintPrice, "Insufficient payment");
        require(_tokenIds.current() < maxSupply, "Max supply reached");

        uint256 platformFee = (msg.value * 5) / 100; // 5% platform fee
        uint256 creatorPayment = msg.value - platformFee;

        // Send platform fee to launchpad
        payable(launchpad).transfer(platformFee);
        // Send remaining amount to creator
        payable(creator).transfer(creatorPayment);

        _tokenIds.increment();
        _safeMint(msg.sender, _tokenIds.current());
    }

    function setBaseURI(string memory _newBaseURI) external {
        require(msg.sender == creator, "Only creator can set URI");
        baseURI = _newBaseURI;
    }

    function _baseURI() internal view override returns (string memory) {
        return baseURI;
    }
}

Gas Optimization Deep Dive ⛽

Our implementation uses several gas optimization techniques:

1. Minimal Proxy Pattern (EIP-1167)

   • Traditional deployment: ~2M gas

   • Clone deployment: ~45k gas

   • Savings: ~97% gas reduction

2. Immutable Variables

   • implementationContract marked as immutable

   • Saves gas by avoiding storage reads

3. Efficient Storage Layout

   • Grouped similar-sized variables

   • Uses packing where possible

   • Minimizes storage slots

Let's verify these savings with a test:

const { expect } = require("chai");

describe("NFT Launchpad Gas Comparison", function () {
  let factory;
  let creator;

  beforeEach(async function () {
    [owner, creator] = await ethers.getSigners();

    const Factory = await ethers.getContractFactory("NFTLaunchpadFactory");
    factory = await Factory.deploy();
    await factory.deployed();
  });

  it("Should show gas savings with clones", async function () {
    const creationFee = ethers.utils.parseEther("0.1");

    // Create first collection
    const tx1 = await factory.connect(creator).createCollection(
      "Test Collection 1",
      "TEST1",
      ethers.utils.parseEther("0.1"),
      100,
      { value: creationFee }
    );
    const receipt1 = await tx1.wait();

    // Create second collection
    const tx2 = await factory.connect(creator).createCollection(
      "Test Collection 2",
      "TEST2",
      ethers.utils.parseEther("0.1"),
      100,
      { value: creationFee }
    );
    const receipt2 = await tx2.wait();

    // Second deployment should use significantly less gas
    expect(receipt2.gasUsed).to.be.lt(receipt1.gasUsed.div(10));
  });
});

Revenue Streams for the Launchpad 💰

1. Creation Fees: 0.1 ETH per collection

2. Platform Fees: 5% of each mint

3. Future Features:

   • Premium listing spots

   • Marketing services

   • Custom features

Security Features 🛡️

Our implementation includes several security measures:

1. Initialization Guard

   • Prevents double initialization

   • Secures proxy pattern

2. Access Control

   • Owner-only fee withdrawal

   • Creator-only URI updates

3. Reentrancy Protection

   • Guards all external calls

   • Secures ETH transfers

4. Event Emissions

   • Tracks all important actions

   • Enables off-chain indexing

What's Next? 🎯

In Part 2, we'll cover:

• Building the React frontend

• Web3 integration

• Collection management

• Minting interface

Conclusion 🌟

We've built a gas-efficient NFT launchpad that saves creators significant deployment costs while maintaining security and functionality. The minimal proxy pattern makes our platform competitive by reducing entry barriers for creators.

Remember to:

1. Test thoroughly

2. Consider a security audit

3. Monitor gas costs

4. Keep implementation contract immutable

Stay tuned for Part 2, where we'll build the frontend! Drop your questions below.

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This is Part 1 of the "Building a Complete NFT Launchpad" series. Follow me to get notified when Part 2 is published!

#NFT #Web3 #Blockchain #Solidity #Programming