In Remix, switch to the DEPLOY & RUN TRANSACTIONS view. You will be very familiar with this by now!
Make sure you are on the fifth icon on the lefthand side of remix
it should be titled DEPLOY & RUN TRANSACTIONS
Make sure you have selected “Injected provider - Metamask” and that the network is (11155111) which is Ethereum Sepolia. If not make sure to switch your network in your Metamask extension.
CrossChainPriceNFT.sol
In the Remix File Explorer, create a new file. Name it CrossChainPriceNFT.sol.
I am providing the code for you here, there were some slight changes in this block of code from the source code used during the Recorded Workshop. Polygon's Mumbai Testnet was deprecated so I took the liberty of updating this code to exclude all references to Mumbai and instead replaced it with parameters that point towards Base Sepolia test network
// SPDX-License-Identifier: MIT
pragma solidity 0.8.19;
// Deploy this contract on Sepolia
// Importing OpenZeppelin contracts
import "@openzeppelin/contracts@4.6.0/token/ERC721/extensions/ERC721URIStorage.sol";
import "@openzeppelin/contracts@4.6.0/utils/Counters.sol";
import "@openzeppelin/contracts@4.6.0/utils/Base64.sol";
// Importing Chainlink contracts
import "@chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";
contract CrossChainPriceNFT is ERC721, ERC721URIStorage {
using Counters for Counters.Counter;
using Strings for uint256;
Counters.Counter public tokenIdCounter;
// Create price feed
AggregatorV3Interface internal priceFeed;
uint256 public lastPrice = 0;
string priceIndicatorUp = unicode"😀";
string priceIndicatorDown = unicode"😔";
string priceIndicatorFlat = unicode"😑";
string public priceIndicator;
struct ChainStruct {
uint64 code;
string name;
string color;
}
mapping (uint256 => ChainStruct) chain;
//https://docs.chain.link/ccip/supported-networks/testnet
constructor() ERC721("CrossChain Price", "CCPrice") {
chain[0] = ChainStruct ({
code: 16015286601757825753,
name: "Sepolia",
color: "#0000ff" //blue
});
chain[1] = ChainStruct ({
code: 14767482510784806043,
name: "Fuji",
color: "#ff0000" //red
});
chain[2] = ChainStruct ({
code: 10344971235874465080,
name: "Base Sepolia",
color: "#4b006e" //purple
});
// https://docs.chain.link/data-feeds/price-feeds/addresses
priceFeed = AggregatorV3Interface(
// Sepolia BTC/USD
0x1b44F3514812d835EB1BDB0acB33d3fA3351Ee43
);
// Mint an NFT
mint(msg.sender);
}
function mint(address to) public {
// Mint from Sepolia network = chain[0]
mintFrom(to, 0);
}
function mintFrom(address to, uint256 sourceId) public {
// sourceId 0 Sepolia, 1 Fuji, 2 Base Sepolia
uint256 tokenId = tokenIdCounter.current();
_safeMint(to, tokenId);
updateMetaData(tokenId, sourceId);
tokenIdCounter.increment();
}
// Update MetaData
function updateMetaData(uint256 tokenId, uint256 sourceId) public {
// Create the SVG string
string memory finalSVG = buildSVG(sourceId);
// Base64 encode the SVG
string memory json = Base64.encode(
bytes(
string(
abi.encodePacked(
'{"name": "Cross-chain Price SVG",',
'"description": "SVG NFTs in different chains",',
'"image": "data:image/svg+xml;base64,',
Base64.encode(bytes(finalSVG)), '",',
'"attributes": [',
'{"trait_type": "source",',
'"value": "', chain[sourceId].name ,'"},',
'{"trait_type": "price",',
'"value": "', lastPrice.toString() ,'"}',
']}'
)
)
)
);
// Create token URI
string memory finalTokenURI = string(
abi.encodePacked("data:application/json;base64,", json)
);
// Set token URI
_setTokenURI(tokenId, finalTokenURI);
}
// Build the SVG string
function buildSVG(uint256 sourceId) internal returns (string memory) {
// Create SVG rectangle with random color
string memory headSVG = string(
abi.encodePacked(
"<svg xmlns='http://www.w3.org/2000/svg' version='1.1' xmlns:xlink='http://www.w3.org/1999/xlink' xmlns:svgjs='http://svgjs.com/svgjs' width='500' height='500' preserveAspectRatio='none' viewBox='0 0 500 500'> <rect width='100%' height='100%' fill='",
chain[sourceId].color,
"' />"
)
);
// Update emoji based on price
string memory bodySVG = string(
abi.encodePacked(
"<text x='50%' y='50%' font-size='128' dominant-baseline='middle' text-anchor='middle'>",
comparePrice(),
"</text>"
)
);
// Close SVG
string memory tailSVG = "</svg>";
// Concatenate SVG strings
string memory _finalSVG = string(
abi.encodePacked(headSVG, bodySVG, tailSVG)
);
return _finalSVG;
}
// Compare new price to previous price
function comparePrice() public returns (string memory) {
uint256 currentPrice = getChainlinkDataFeedLatestAnswer();
if (currentPrice > lastPrice) {
priceIndicator = priceIndicatorUp;
} else if (currentPrice < lastPrice) {
priceIndicator = priceIndicatorDown;
} else {
priceIndicator = priceIndicatorFlat;
}
lastPrice = currentPrice;
return priceIndicator;
}
function getChainlinkDataFeedLatestAnswer() public view returns (uint256) {
(, int256 price, , , ) = priceFeed.latestRoundData();
return uint256(price);
}
function tokenURI(uint256 tokenId)
public view override(ERC721, ERC721URIStorage) returns (string memory)
{
return super.tokenURI(tokenId);
}
// The following function is an override required by Solidity.
function _burn(uint256 tokenId) internal override(ERC721, ERC721URIStorage)
{
super._burn(tokenId);
}
}
We will now deploy the code. Switch to Remix's DEPLOY & RUN TRANSACTIONS tab, select the CrossChainPriceNFT file and click the Deploy button.
We will now check this collection on Opensea.
Copy your CrossChainPriceNFT contract address.
Use this link testnet.opensea.io to navigate the testnet version of Opensea. In the search bar you will search your CrossChainPriceNFT.sol address that you just deployed.
Save this link to your collection so you can check on the status of your NFT's
