Launch and verify an NFT with Foundry

In the video tutorial above, you put an NFT on Opensea using the Remix environment.This is fine, but Remix is not ideal for production use.In this chapter, we will show you how to

1. Set up Foundry with the NFT
2. Deploy it to the Sepolia testnet and verify it on Etherscan

If you’ve been doing the exercises, you should already have foundry installed, so let’s set it up.Create a new folder; call it foundry-nft, cd to it, and run “forge init” in the empty folder.Copy and Paste the codeHere’s the code for creating the NFT. Rename the Counter.sol file in the “src” directory to FoundryNFT.sol and paste this code.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13;

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

contract FoundryNFT is ERC721 {
    uint256 public totalSupply = 0;

    constructor() ERC721("FoundryNFT", "FNFT") {}

    function mint() 
            external 
            payable {
                    // you can add a price check here if you like
                    totalSupply++;
                    _mint(msg.sender, totalSupply);
    }
}

Installing OpenzeppelinWe import and inherit the Openzepplin ERC721 contract, so to install it use the following:

forge install Openzeppelin/openzeppelin-contracts --no-commit

Using remappingsComing from a Remix background, you’ll notice that the OpenZeppelin import path here differs. Remix doesn’t store libraries in the same location Foundry does. However, Foundry provides remappings to allow file lookups on import to be redirected to a different location.To see all the available remappings, we run forge remappings.We get this:

ds-test/=lib/forge-std/lib/ds-test/src/
forge-std/=lib/forge-std/src/
openzeppelin-contracts/=lib/openzeppelin-contracts/

We can see the OpenZepplin remapping, so we don’t need to specify the full path to the OpenZeppelin contracts. We can use openzeppelin-contracts/contracts/token/ERC721/ERC721.sol instead of specifying the “lib/” directory first.Not using remappingsIf we were not using forge remappings, we would have to specify the full path to our files or directories.For example, for the ERC721.sol file, we would do something like this to import it.

import "lib/openzeppelin-contracts/contracts/token/ERC721/ERC721.sol";

To confirm this is still valid, run forge build and see if it compiles.And it does

[⠰] Compiling...
[⠃] Compiling 1 files with 0.8.17
[⠊] Solc 0.8.17 finished in 1.38s
Compiler run successful

Now undo the changes back to how it was.

Generating the remappings.txt file in one step

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This can be done with the following operation

forge remappings > remappings.txt

Change the file namesWe can further configure where the remappings point by creating a remappings.txt file in the project root directory and adding this line @openzeppelin=lib/openzeppelin-contracts/contracts to the file.After doing this, we can use import “@openzeppelin/token/ERC721/ERC721.sol”; to import the ERC721 token instead of explicitly writing the full file path.This remapping can be configured in the remappings.txt file if it points to the right path.Getting an Etherscan keyWhen we deploy our NFT, we need an Etherscan API to verify the contract. This will let us easily connect to Etherscan to verify the smart contract using forge without going to the Etherscan website and following the process.Head to Etherscan, log in, and create an API key.We have created U3D9IS6Z5E872VFS7M7AWR1SBA8786ZZ3Y as our API key. We’ll be using this API key later.

Creating a throwaway wallet

Never use the private keys to a hardware wallet or any wallet that holds significant value.To deploy the NFT contract to the testnet, we need a private key with test ether to sign the transaction.For the sake of simplicity, we have created a throwaway wallet and funded it with some sepolia ether.Here’s the private key of the wallet; 787ea4ec95ab4f4e66c4c4c387cd0b5fbbec84a9293db485fa5f86f490c157d4.

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(This shouldn’t be used as it is considered comprised already.)

Put the Etherscan key and private key of the wallet in your environment variables

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Now that we have both our API key and private key, the next step is to create a .env file in the project’s root directory and add this to it.

ETHERSCAN_KEY=U3D9IS6Z5E872VFS7M7AWR1SBA8786ZZ3Y #you can replace this with your API key
PRIVATE_KEY=787ea4ec95ab4f4e66c4c4c387cd0b5fbbec84a9293db485fa5f86f490c157d4

Make sure your .env file is included in your .gitignore so you don’t accidentally publish your private keys!

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Run this script

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Run this script to deploy and verify the NFT contract on sepolia.

source .env #load the environment variables

forge create --rpc-url https://rpc2.sepolia.org --private-key $PRIVATE_KEY --etherscan-api-key $ETHERSCAN_KEY --verify src/FoundryNFT.sol:FoundryNFT 

View on EtherscanWe have successfully deployed our NFT contract on the sepolia testnet.

• The transaction hash
• The verified contract