Deploy contracts within contracts

Deploying contracts within contracts allows more flexibility and allows to separate or transfer control in certain situations.

This example shows how to deploy another contract and interact with it.

Contract to deploy

Based on the OpenZeppelin Wizard a tiny NFT contract looks like this:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;
 
import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
 
contract NFT is ERC721, Ownable {
    constructor() ERC721("NFT", "MTK") {}
}

To demonstrate dynamic parameters the constructor is adjusted to set name & symbol during deployment:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;
 
import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
 
contract NFT is ERC721, Ownable {
    constructor(string memory name, string memory symbol)
        ERC721(name, symbol)
    {}
}

The Factory

Deploying new contracts is automatically done when a new instance is created with thenew keyword:

NFT createdContract = new NFT("name", "symbol")

Interaction is immediately possible with the instance. The address is available using the address function:

address contractAddress = address(createdContract);

The complete deployment code is:

import "./NFT.sol";
 
contract Factory {
    function createContract(string memory name, string memory symbol)
        public
        returns (address)
    {
            // deploy new contract
        NFT createdContract = new NFT(name, symbol);
        
        // get contract address for further use
        address contractAddress = address(createdContract);
 
                // interact with the new contract
        createdContract.transferOwnership(msg.sender);
 
        return contractAddress;
    }
}

Example Project

The full working example with more details is available on GitLab: https://gitlab.com/vechain.energy/examples/contract-in-contract/-/tree/master/ (opens in a new tab)

Base64 Outputs Swap Tokens in Contracts