Calling contracts with the Unity SDK

Smart contracts are backend programs that run on the Tezos blockchains. Smart contracts can do many tasks, but for gaming they have two main purposes:

• They handle tokens, which are digital assets stored on the blockchain
• They provide backend logic that users can trust because it cannot change

For more information about contracts, see Smart contracts.

The Unity SDK can call any deployed Tezos contract just like any other Tezos client can.

Calling contracts

Smart contracts have one or more entrypoints, which are the different ways that it can be called, similar to a method or function in programming languages or an endpoint in an API. Therefore, to call a smart contract, you need:

• Its address, which starts with KT1
• The entrypoint to call
• The parameter to pass to the entrypoint, which must be in the format that the entrypoint expects
• An amount of tez tokens to send with the transaction, which can be zero or more

To call a contract, create an OperationRequest object with that information and pass it to the TezosAPI.RequestOperation() method. For example, this code calls a contract and passes the parameter 5 to its increment entrypoint. When the transaction completes successfully, it logs the hash of the transaction. You can use this hash to look up information about the transaction in a block explorer.

private async void Awake()
{
    await TezosAPI.WaitUntilSDKInitialized();

    _connectButton.onClick.AddListener(OnConnectClicked);
    _disconnectButton.onClick.AddListener(OnDisconnectClicked);
    _requestOperationButton.onClick.AddListener(OnRequestOperationClicked);

    TezosAPI.OperationResulted += OperationResulted;
}

private async void OnRequestOperationClicked()
{
    try
    {
        var request = new OperationRequest
        {
            // Contract to call
            Destination = "KT1R2LTg3mQoLvHtUjo2xSi7RMBUJ1sJkDiD",
            // Entrypoint to call
            EntryPoint = "increment",
            // Parameter to pass, as a Michelson expression
            Arg = new MichelineInt(5).ToJson(),
            // Amount of tez to send with the transaction
            Amount = "0",
        };
        var response = await TezosAPI.RequestOperation(request);
    }
    catch (Exception e) when (e is WalletOperationRejected or SocialOperationFailed)
    {
        Debug.LogError($"Operation failed: {e.Message}");
    }
    catch (Exception e)
    {
        Debug.LogError($"Unexpected error during operation: {e.Message}");
    }
}

private void OperationResulted(OperationResponse operationResponse)
{
    Debug.Log("Transaction hash: " + operationResponse.TransactionHash);
}

Calling views

To call a view, pass the address of the contract, the name of the view, and the Michelson-encoded parameter to the TezosAPI.ReadView() method. You must set the return type on the TezosAPI.ReadView() method, as in this example for a view that returns a string:

var result = await TezosAPI.ReadView<string>("KT1K46vZTMEe8bnacFvFQfgHtNDKniEauRMJ", "simple", "\"String value\"");
Debug.Log("View response: " + result);