How to Create a New Contract Using Solidity: A Step-by-Step Guide

Introduction

Solidity's new keyword enables developers to deploy new contract instances from templates. The "XxxContractFactory" naming convention represents a design pattern where a factory contract creates instances of an "XxxContract".

This guide explores:

The fundamentals of contract factories
Implementation mechanics
Practical applications like:
- Liquidity pool creation (Uniswap)
- NFT minting strategies (Adidas 2 NFT case)
- No-code token platforms (ThirdWeb)

Core Implementation

1. Template Contract (Bank.sol)

contract Bank {
    uint256 public bank_funds;
    address public owner;
    address public deployer;
    
    constructor(address _owner, uint256 _funds) {
        bank_funds = _funds;
        owner = _owner;
        deployer = msg.sender;
    }
}

2. Factory Contract (BankFactory.sol)

contract BankFactory {
    Bank[] public list_of_banks;
    
    function createBank(address _owner, uint256 _funds) external {
        Bank bank = new Bank(_owner, _funds);
        list_of_banks.push(bank);
    }
}

Key components:

new Bank(_owner, _funds) deploys new instances
Dynamic array tracks deployed contracts

Testing with HardHat

Setup

Initialize project:

npm install --save-dev hardhat
npx hardhat

Add this test script:

describe("BankFactory Deployment", () => {
 it("Should create multiple Bank instances", async () => {
     const BF = await ethers.getContractFactory('BankFactory');
     const bf = await BF.deploy();
     
     await bf.createBank("0x0d8D...6666", 69420);
     const bankAddress = await bf.list_of_banks(0);
     
     // Verify deployment
     const bank = await ethers.getContractAt("Bank", bankAddress);
     console.log(`Bank funds: ${await bank.bank_funds()}`); 
 });
});

Key Use Cases

Application	Example Protocol
Decentralized Finance	Uniswap Factories
NFT Collections	Adidas 2
Tokenization	ThirdWeb

FAQ

Q: Why use factory contracts?
A: They enable scalable deployment while reducing gas costs through template reuse.

Q: Can factories call external contracts?
A: Yes, but ensure proper security checks with OpenZeppelin libraries.

Q: How to track deployed contracts?
A: Use dynamic arrays or mappings in the factory contract.

👉 Master Smart Contract Development