How to design a cross-chain NFT smart contract
gasLimitextraArgsfunction crossChainTransferFrom(
address from,
address to,
uint256 tokenId,
uint64 destinationChainSelector,
PayFeesIn payFeesIn
)
external
nonReentrant
onlyEnabledChain(destinationChainSelector)
returns (bytes32 messageId)
{
string memory tokenUri = tokenURI(tokenId);
// Burning token on source blockchain
_burn(tokenId);
Client.EVM2AnyMessage memory message = Client.EVM2AnyMessage({
receiver: abi.encode(
s_chains[destinationChainSelector].xNftAddress
),
// Encoding details for minting on the destination blockchain
data: abi.encode(from, to, tokenId, tokenUri),
tokenAmounts: new Client.EVMTokenAmount[](0),
extraArgs: s_chains[destinationChainSelector].ccipExtraArgsBytes,
feeToken: payFeesIn == PayFeesIn.LINK
? address(i_linkToken)
: address(0)
});
}function ccipReceive(
Client.Any2EVMMessage calldata message
)
external
virtual
override
onlyRouter
nonReentrant
onlyEnabledChain(message.sourceChainSelector)
onlyEnabledSender(
message.sourceChainSelector,
abi.decode(message.sender, (address))
)
{
(
address from,
address to,
uint256 tokenId,
string memory tokenUri
) = abi.decode(message.data, (address, address, uint256, string));
_safeMint(to, tokenId);
_setTokenURI(tokenId, tokenUri);
}// struct XNftDetails {
address xNftAddress;
bytes ccipExtraArgsBytes;
}
mapping(uint64 destChainSelector => XNftDetails xNftDetailsPerChain)
public s_chains;
modifier onlyEnabledChain(uint64 _chainSelector) {
if (s_chains[_chainSelector].xNftAddress == address(0))
revert ChainNotEnabled(_chainSelector);
_;
}
modifier onlyEnabledSender(uint64 _chainSelector, address _sender) {
if (s_chains[_chainSelector].xNftAddress != _sender)
revert SenderNotEnabled(_sender);
_;
}
function enableChain(
uint64 chainSelector,
address xNftAddress,
bytes memory ccipExtraArgs
) external onlyOwner onlyOtherChains(chainSelector) {
s_chains[chainSelector] = XNftDetails({
xNftAddress: xNftAddress,
ccipExtraArgsBytes: ccipExtraArgs
});
emit ChainEnabled(chainSelector, xNftAddress, ccipExtraArgs);
}
function disableChain(
uint64 chainSelector
) external onlyOwner onlyOtherChains(chainSelector) {
delete s_chains[chainSelector];
emit ChainDisabled(chainSelector);
}// EncodeExtraArgs.s.sol
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.19;
import {Client} from "@chainlink/contracts-ccip/src/v0.8/ccip/libraries/Client.sol";
contract EncodeExtraArgs {
// Below is a simplistic example (same params for all messages) of using storage to allow for new options without
// upgrading the dapp. Note that extra args are chain family specific (e.g. gasLimit is EVM specific etc.).
// and will always be backwards compatible i.e. upgrades are opt-in.
// Offchain we can compute the V1 extraArgs:
// Client.EVMExtraArgsV1 memory extraArgs = Client.EVMExtraArgsV1({gasLimit: 300_000});
// bytes memory encodedV1ExtraArgs = Client._argsToBytes(extraArgs);
// Then later compute V2 extraArgs, for example if a refund feature was added:
// Client.EVMExtraArgsV2 memory extraArgs = Client.EVMExtraArgsV2({gasLimit: 300_000, destRefundAddress: 0x1234});
// bytes memory encodedV2ExtraArgs = Client._argsToBytes(extraArgs);
// and update storage with the new args.
// If different options are required for different messages, for example different gas limits,
// one can simply key based on (chainSelector, messageType) instead of only chainSelector.
function encode(
uint256 gasLimit
) external pure returns (bytes memory extraArgsBytes) {
Client.EVMExtraArgsV1 memory extraArgs = Client.EVMExtraArgsV1({
gasLimit: gasLimit
});
extraArgsBytes = Client._argsToBytes(extraArgs);
}
}
