Skip to main content

Managing contracts

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.

You can create your own smart contracts or use the built-in contract that the SDK provides for managing tokens in Unity projects.

The Contract example scene shows how to deploy a copy of the built-in contract from a Unity project.

The built-in contract​

The SDK includes a built-in contract that you can use to manage tokens for your Unity projects.

The contract has entrypoints that allow you to create and transfer tokens. See Managing tokens.

The Michelson source code of the built-in contract is in the Resources/Contracts folder of the SDK, but it isn't very human-readable. For a list of the entrypoints in the contract, see TokenContract object.

Deploying the built-in contract​

To deploy the built-in contract, call the TokenContract.Deploy() method and pass a callback function:

public void DeployContract()
{
    TezosManager
        .Instance
        .Tezos
        .TokenContract
        .Deploy(OnContractDeployed);
}

private void OnContractDeployed(string contractAddress)
{
    Debug.Log(contractAddress);
}

The project sends the deployment transaction to the connected wallet, which must approve the transaction and pay the related fees. The callback function receives the address of the deployed contract, which the project uses to send requests to the contract. It can take a few minutes for the contract to deploy and be confirmed in multiple blocks on the blockchain.

The address that deployed the contract becomes the administrator of the contract and is the only account that can create tokens.

The SDK provides information about the contract such as its address in the TokenContract object. You can use block explorers such as Better Call Dev to see information about the deployed contract.

For information about using the built-in contract, see Managing tokens.

Getting the contract address​

When you deploy a contract with the TokenContract.Deploy() method, the SDK saves the contract address by running this code:

PlayerPrefs.SetString("CurrentContract:" + Tezos.Wallet.GetActiveAddress(), contractAddress);

Then during SDK initialization, the SDK saves the address to the TokenContract.Address property.

To retrieve the address of contracts that you haven't deployed through the project, you can use the API.GetOriginatedContractsForOwner() method or use another way of getting the contract address.

Calling the built-in contract​

The built-in contract has convenience methods for minting and transferring tokens; see Managing tokens.

To call the contract's other entrypoints, use the Wallet.CallContract() method. For example, to call the contract's set_administrator entrypoint to set a new administrator account, use this code:

using Netezos.Contracts;
using Netezos.Encoding;
using Newtonsoft.Json.Linq;

// ...

// Use Michelson JSON of the contract code
var contractJSON = Resources.Load<TextAsset>("Contracts/FA2TokenContract").text;
var code = JObject
    .Parse(contractJSON)
    .SelectToken("code");

// Create a `Netezos.Contracts.ContractScript` object to represent the contract
var contract = new ContractScript(Micheline.FromJson(code.ToString()));

// Build the parameters for the call
var callParameters = contract.BuildParameter(
    entrypoint: "set_administrator",
    value: newAdministratorAddress
).ToJson();

// Call the contract
TezosManager.Instance.Tezos.Wallet.CallContract(
    contractAddress: contractAddress,
    entryPoint: "set_administrator",
    input: callParameters
);

For information about the entrypoints in the built-in contract, see Unity SDK TokenContract object.

Deploying other contracts​

To deploy a contract from Unity, you must compile the contract to Michelson in JSON format. For example, to compile a contract in LIGO to Michelson JSON, run this code:

ligo compile contract MyContract.jsligo \
  -m MyContract -o MyContract.json --michelson-format json

Then, ensure that the code of the code and initial storage value of the contract are wrapped in code and storage fields at the root of the file, as in this example:

{
  "code": [
    {
      "prim": "parameter",
      "args": [
        ...
    },
  ],
  "storage": {
    "int": "0"
  }
}

To deploy the contract from the Unity project, use the Wallet.OriginateContract() method, as in this example:

var contractJSON = Resources.Load<TextAsset>("Contracts/MyContract").text;
TezosManager.Instance.Tezos.Wallet.OriginateContract(contractJSON);

To get the address of the deployed contract, use the ContractCallCompleted event.

Calling other contracts​

The built-in contract provides convenience methods that you can use to interact with it. See Managing tokens.

To call any other contract, you need its source code in Michelson JSON format. You can retrieve the code of a deployed contract from block explorers or APIs such as the TZKT API.

Then you can call the contract by assembling a Netezos.Contracts.ContractScript object that represents the contract and building an object out of the entrypoint to call and the value to pass to it, as in this example:

using Netezos.Contracts;
using Netezos.Encoding;
using Newtonsoft.Json.Linq;

// ...

// Use Michelson JSON of the contract code
var contractJSON = Resources.Load<TextAsset>("Contracts/MyContract").text;
var code = JObject
    .Parse(contractJSON)
    .SelectToken("code");

// Create a `Netezos.Contracts.ContractScript` object to represent the contract
var contract = new ContractScript(Micheline.FromJson(code.ToString()));

// Build the parameters for the call
var callParameters = contract.BuildParameter(
    entrypoint: entryPointName,
    value: 12
).ToJson();

// Call the contract
TezosManager.Instance.Tezos.Wallet.CallContract(
    contractAddress: address,
    entryPoint: entryPointName,
    input: callParameters
);

This example passes the value 12 to the entrypoint in the variable entryPointName. If the entrypoint requires a parameter that is more complex than a single value, you must encode it as described in Encoding parameters.

To get the hash of the transaction, use the ContractCallCompleted event.

Encoding parameters​

When you call contract entrypoints or views with Wallet.CallContract(), you must encode the parameter as a Micheline value. For example, if an entrypoint accepts four integers as parameters, you must pass a list of Netezos.Encoding.MichelineInt values:

TODO can't get this to work with various values.

Last updated on