• Unity SDK
  • Interact with Blockchain
  • Update NFT

Update an NFT

Making updates to the NFT, e.g. adding a red hat to a character requires signing and sending a transaction.

Signing transactions

All updates are transactions that must be signed via a prompt from MetaMask.

Sending transactions

There are two ways to make update transactions: Using the GetData method and the CallMethod

GetData method

Use the GetData method to retrieve information from the blockchain. (READ functions do NOT require mining.). Other non-standard Get functions are also available

These methods require:

  • Contract Address
  • ABI

The following extract is an example usage of the GetData method to retrieve information about an NFT:

private async UniTask<BigInteger> GetHat(BigInteger tokenID)
			var getHatMessage = new GetHatMessage
				CharacterId = tokenID.ToString()
			var hatId = await _gameCharacterContract.GetData<GetHatMessage, BigInteger>(getHatMessage);

			UpdateUILogs($"Hat Id: {hatId}");

			return hatId;


Use the CallMethod to write new information to the blockchain. These methods utilize gas.

The following extract is an example of how a CallMethod is used to update an NFT:

public async void UpdateNFT()
			// 1) Request nft parameters and signature for parameters
			var info = await RequestPreparedParams(0);
			// 2) Call method that check signature and update nft
			var receipt = await _contract.CallMethod("updateTokenWithSignedMessage", new object[] { info });

			Debug.Log($"Receipt: {receipt}");

Example: update NFT

This is an example from the SDK and illustrates how to update a GameItem NFT by user request.

  1. Amend GameItem.sol to your purposes and deploy it to the network.


    Ensure that the smart contract is deployed from the same account that uses the backend to sign data.

  2. Create an instance of Web3 class and call Initialize method after logging in MetaMask

    string provider_url = "<ethereum node url>";
    Web3 web3 = new Web3(provider_url);
  3. The user sends a GET request hero/{id} to backend where id is the index of the NFT in the contract.

    UnityWebRequest request = UnityWebRequest.Get(url+$"hero/{tokenId}");
    await request.Send();
  4. The Backend prepares parameters for the hero NFT and signs it with EIP-712 standard. The user implements this signature to prove immutability of the data in the contract.

    hero := &ItemInfo{
        TokenId:    id,
        ItemType:   1,
        Strength:   10,
        Level:      15,
        ExpireTime: 1642739319576,
    hero.Signature = generateSignature(*hero)
  5. After getting the parameters of the NFT and Signature, the user should call contract method updateTokenWithSignedMessage and pass it all data from the backend as tuple.

    ItemInfo info = await RequestPreparedParams(0);
    string receipt = await contract.CallMethod("updateTokenWithSignedMessage", new object[] {info});
  6. The Contract verifies the signature and expireTime for data and updates the NFT.

    function updateTokenWithSignedMessage(ItemInfo calldata itemInfo) public {
        address signer = _verifyItemInfo(itemInfo);
        require(hasRole(UPDATER_ROLE, signer), "Signature invalid");
        require(itemInfo.expireTime > block.timestamp, "Voucher expired");
        require(tokenDetails[itemInfo.tokenId].itemType > 0, "Token does not exist");
        tokenDetails[itemInfo.tokenId] = Item(itemInfo.itemType, itemInfo.strength, itemInfo.level);