A Smart Contract is a program that is stored and executed on the blockchain. It contains the NFT's metadata, such as the name of the NFT, a URL to the NFT data file, a description of the NFT, and any other data the creator has included. If the NFT is part of a collection, sometimes there will be metadata stating its position in the collection and its rarity compared to other NFTs in the collection.
What is Metadata?
Metadata is simply data that provides additional data about other data. Metadata of an object stored on Filebase typically includes the owner’s account email, size, ETag, object key or name, time and date last modified, and if the object is stored on an IPFS bucket, the IPFS CID is included in the object’s metadata.
In this guide, we’ll use Truffle, Ganache, and Infura to create a local development environment using the Ropsten blockchain network that enables us to use a series of scripts to mint NFTs and their metadata using a single command and their IPFS CID.
Prerequisites:
This guide was written and tested using Ubuntu 20.04. Commands and workflow may vary depending on your operating system.
1. First, we need to upload the NFT image files to IPFS through Filebase.
For this project, we’ll be uploading 3 images to Filebase for us to use. To do this, navigate to . If you don’t have an account already, , then log in.
2. Select ‘Buckets’ from the left side bar menu, or navigate to.
Select ‘Create Bucket’ in the top right corner to create a new bucket for your NFTs.
3. Enter a bucket name and choose the IPFS storage network to create the bucket.
Bucket names must be unique across all Filebase users, be between 3 and 63 characters long, and can contain only lowercase characters, numbers, and dashes.
4. Next, select the bucket from your list of buckets, then select ‘Upload’ in the top right corner to upload your image files.
5. Select your images to be uploaded.
Once uploaded, they will be listed in the bucket.
6. Click on each uploaded object to display the metadata for the object.
Take note of the IPFS CID for each object.
7. Next, create a new directory for your project’s files and navigate inside of that directory.
mkdir nft-factory
cd nft-factory
8. Initialize your npm workspace:
npm init
Provide any necessary configuration options for your workspace, or accept the default configuration settings for your npm workspace.
9. Install Truffle and Ganche into your project:
npm install -g truffle
npm install ganache --global
10. Unbox the truffle package:
truffle unbox react
Your project will have the following files and directories:
contracts/
migrations/
test/
truffle-config.js
Do not remove any of the files that already exist in these directories, such as Migrations.sol or SimpleStorage.sol.
11. Navigate into the contracts directory.
Then, open an IDE such as VSCode, and enter the following piece of code into a new file called nftFactory.sol in your contracts directory:
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.1;
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721URIStorage.sol";
import "@openzeppelin/contracts/utils/Counters.sol";
contract nftFactory is ERC721URIStorage {
using Counters for Counters.Counter;
Counters.Counter private _tokenIds;
event CreatedNFT(uint256 indexed tokenId, string tokenURI);
constructor() ERC721("My NFT Collection", "MNC") {}
function mint(string memory _tokenURI) public returns (uint256) {
uint256 newItemId = _tokenIds.current();
_safeMint(msg.sender, newItemId);
_setTokenURI(newItemId, _tokenURI);
emit CreatedNFT(newItemId, _tokenURI);
_tokenIds.increment();
return newItemId;
}
}
This code imports the ERC721 token standard using an open source contract from Openzeppelin. Then, it creates the function that is responsible for minting our contract, which is a public function, meaning it can be called by any contract or wallet address, though whoever calls the function will be paying the gas fees.
13. Select the Ethereum network, and give your project a name.
14. In the Project settings, select "Ropsten” from the endpoint dropdown menu.
15. Then, take down the Project ID. You will need this in the next step.
16. Open the truffle-config.js file and replace the contents with the following content:
const path = require("path");
module.exports = {
// See <http://truffleframework.com/docs/advanced/configuration>
// to customize your Truffle configuration!
compilers:{
solc: {
version: "0.8.1",
optimizer: {
enabled: true,
runs: 200
}}},
contracts_build_directory: path.join(__dirname, "client/src/contracts"),
networks: {
development:{ host: "127.0.0.1",
port: 8545, network_id: "*" // Match any network id
},
ropsten:{
provider: function() {
return new HDWalletProvider(mnemonic, // Project secret key
"https://ropsten.infura.io/v3/INFURA_PROJECT_ID")
}},
}
};
Replace the INFURA_PROJECT_ID with the project ID you copied down in the last step.
17. In the migrations directory, update the existing file 2_deploy_contracts.js with the following content:
var nftFactory = artifacts.require("./nftFactory.sol");
module.exports = function(deployer) {
deployer.deploy(nftFactory);
};
18. Next, launch the Truffle development console with the command:
truffle develop
19. Deploy all the contracts with the command:
migrate –-reset
Your output should resemble the following:
truffle(develop)> migrate --reset
Compiling your contracts...
===========================
> Compiling ./contracts/nftFactory.sol
> Artifacts written to /home/filebase/client/src/contracts
> Compiled successfully using:
- solc: 0.8.1+commit.df193b15.Emscripten.clang
Starting migrations...
======================
> Network name: 'develop'
> Network id: 5777
> Block gas limit: 6721975 (0x6691b7)
1_initial_migration.js
======================
Replacing 'Migrations'
----------------------
> transaction hash: 0xbb354a7275da5af90f0ff462bbbcfbdfb529554cdb7cc2432541bb16668aac17
> Blocks: 0 Seconds: 0
> contract address: 0x6aaea605d6a1e07BD1A2cd7CAe6dE8dB569aa5FB
> block number: 25
> block timestamp: 1646682139
> account: 0x2D99E145805912f2964b4A8636291133fe03e4Ba
> balance: 99.99007346984352138
> gas used: 271700 (0x42554)
> gas price: 2.540819307 gwei
> value sent: 0 ETH
> total cost: 0.0006903406057119 ETH
> Saving migration to chain.
> Saving artifacts
-------------------------------------
> Total cost: 0.0006903406057119 ETH
2_deploy_contracts.js
=====================
Deploying 'nftFactory'
----------------------
> transaction hash: 0xe21306f9915ba9509bcfab324037c10e5616860e42ad9687e64b9cee023e2e69
> Blocks: 0 Seconds: 0
> contract address: 0x4Dd6153057B939b882992fa96F529687ba7a60a0
> block number: 27
> block timestamp: 1646682140
> account: 0x2D99E145805912f2964b4A8636291133fe03e4Ba
> balance: 99.983540351487302762
> gas used: 2534533 (0x26ac85)
> gas price: 2.531674926 gwei
> value sent: 0 ETH
> total cost: 0.006416613645219558 ETH
> Saving migration to chain.
> Saving artifacts
-------------------------------------
> Total cost: 0.006416613645219558 ETH
Summary
=======
> Total deployments: 2
> Final cost: 0.007106954250931458 ETH
20. In your Truffle console, use the following command to create a new instance of your contract:
let nft = await nftFactory.deployed();
21. Then, in the same Truffle console, mint your NFTs.
Replace the IPFS_CID with one of the IPFS CIDs you recorded from your Filebase upload at the beginning of this tutorial.
