MyEpicNFT.sol

pragma solidity 0.8.0;

// We need some util functions for strings.
import "@openzeppelin/contracts/utils/Strings.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721URIStorage.sol";
import "@openzeppelin/contracts/utils/Counters.sol";
import "hardhat/console.sol";


contract MyEpicNFT is ERC721URIStorage {
  using Counters for Counters.Counter;
  Counters.Counter private _tokenIds;

  // This is our SVG code. All we need to change is the word that's displayed. Everything else stays the same.
  // So, we make a baseSvg variable here that all our NFTs can use.
  string baseSvg = "<svg xmlns='http://www.w3.org/2000/svg' preserveAspectRatio='xMinYMin meet' viewBox='0 0 350 350'><style>.base { fill: white; font-family: serif; font-size: 24px; }</style><rect width='100%' height='100%' fill='black' /><text x='50%' y='50%' class='base' dominant-baseline='middle' text-anchor='middle'>";

  // I create three arrays, each with their own theme of random words.
  // Pick some random funny words, names of anime characters, foods you like, whatever! 
  string[] firstWords = ["YOUR_WORD", "YOUR_WORD", "YOUR_WORD", "YOUR_WORD", "YOUR_WORD", "YOUR_WORD"];
  string[] secondWords = ["YOUR_WORD", "YOUR_WORD", "YOUR_WORD", "YOUR_WORD", "YOUR_WORD", "YOUR_WORD"];
  string[] thirdWords = ["YOUR_WORD", "YOUR_WORD", "YOUR_WORD", "YOUR_WORD", "YOUR_WORD", "YOUR_WORD"];

  constructor() ERC721 ("SquareNFT", "SQUARE") {
    console.log("This is my NFT contract. Woah!");
  }

  // I create a function to randomly pick a word from each array.
  function pickRandomFirstWord(uint256 tokenId) public view returns (string memory) {
    // I seed the random generator. More on this in the lesson. 
    uint256 rand = random(string(abi.encodePacked("FIRST_WORD", Strings.toString(tokenId))));
    // Squash the # between 0 and the length of the array to avoid going out of bounds.
    rand = rand % firstWords.length;
    return firstWords[rand];
  }

  function pickRandomSecondWord(uint256 tokenId) public view returns (string memory) {
    uint256 rand = random(string(abi.encodePacked("SECOND_WORD", Strings.toString(tokenId))));
    rand = rand % secondWords.length;
    return secondWords[rand];
  }

  function pickRandomThirdWord(uint256 tokenId) public view returns (string memory) {
    uint256 rand = random(string(abi.encodePacked("THIRD_WORD", Strings.toString(tokenId))));
    rand = rand % thirdWords.length;
    return thirdWords[rand];
  }

  function random(string memory input) internal pure returns (uint256) {
      return uint256(keccak256(abi.encodePacked(input)));
  }

  function makeAnEpicNFT() public {
    uint256 newItemId = _tokenIds.current();

    // We go and randomly grab one word from each of the three arrays.
    string memory first = pickRandomFirstWord(newItemId);
    string memory second = pickRandomSecondWord(newItemId);
    string memory third = pickRandomThirdWord(newItemId);

    // I concatenate it all together, and then close the <text> and <svg> tags.
    string memory finalSvg = string(abi.encodePacked(baseSvg, first, second, third, "</text></svg>"));
    console.log("\n--------------------");
    console.log(finalSvg);
    console.log("--------------------\n");

    _safeMint(msg.sender, newItemId);
  
    // We'll be setting the tokenURI later!
    _setTokenURI(newItemId, "blah");
  
    _tokenIds.increment();
    console.log("An NFT w/ ID %s has been minted to %s", newItemId, msg.sender);
  }
}

pragma solidity 0.8.0; => pragma solidity ^0.8.0;

Don't forget to add the first line: // SPDX-License-Identifier: UNLICENSED

Correct, i think it's good to add // SPDX-License-Identifier: UNLICENSED at the top of the file, but for learning purposes, it's okay to omit.

// SPDX-License-Identifier: UNLICENSED

pragma solidity ^0.8.1;

Why did we step down to pragma solidity 0.8.0; from pragma solidity ^0.8.1; ?

Change pragma solidity 0.8.0; => pragma solidity ^0.8.0;

Also add: // SPDX-License-Identifier: MIT to first line

Why use keccak256 instead of sha256?

Perfect for use with above changes >