How to do Primary Sales for On-Chain Items in Unity

Accelerate your game growth by selling items directly to your players. In this guide, we will go over the steps how to deploy a Primary Sale contract using any custom or existing currency for an In-Game Shop that utilizes game items from a ERC1155 contract. We will use the following technologies from the Sequence platform:

• Primary Sales Contract: How to set up and deploy contracts for launching a primary sale — suitable for an Web Shop, NFT Drop, and more.
• Sequence Indexer: Leveraging the Sequence Indexer to query NFT metadata and user's wallet assets.

1. Deploy your own Token- and Sale Contract in Sequence Builder

We first need a Primary Sales Contract along with an ERC1155 contract that will contain our game items we want to sell. To do that, please follow the guide here.

2. Use the Primary Sales Demo inside Sequence's Unity SDK

To get started, import Sequence's Unity SDK into your project. Then, navigate to the Demo.unity scene located Sequence Embedded Wallet SDK/Sequence/Samples/DemoScene. In this scene, you’ll find the PrimarySalePage object, which serves as a useful reference.

3. Set your Sale Configurations in your Project

To configure your sale, use the PrimarySalePage object to input your sale information. In the Configuration section, you’ll find the following options:

• Chain: Select the chain where your contract is deployed.
• Token & Sale Contract Address: Enter the contract addresses provided by Sequence's Builder.
• Items For Sale: List all the Token IDs you wish to sell.

4. Implement Custom Code to Interact with the SDK

Let's create a custom class to manage the state for our sale. This class will gather all the necessary data, allowing us to display this information to users effectively. In the PrimarySalePage.cs demo, the data is sourced from the Configuration section.

class ERC1155SaleState;
 
public ERC1155SaleState(IWallet wallet, string tokenContractAddress, string saleContractAddress, Chain chain, int[] itemsForSale)
{
    _tokenContractAddress = tokenContractAddress;
    _saleContract = new ERC1155Sale(saleContractAddress);
    _client = new SequenceEthClient(chain);
    _wallet = wallet;
    _chain = chain;
    _itemsForSale = itemsForSale;
}

5. Retrieve Your Primary Sale Details

Next, use the ERC1155Sale.cs reference to obtain sale details and the payment token from the contract. This information can be used, for instance, to locally verify if the user has sufficient balance for the specified payment token.

public async Task<bool> UpdateSaleDetailsAsync()
{
    string paymentToken = await _saleContract.GetPaymentTokenAsync(_client);
 
    ERC1155Sale.SaleDetails globalSaleDetails = await _saleContract.GetGlobalSaleDetailsAsync(_client);
    BigInteger cost = globalSaleDetails.Cost;
    BigInteger supplyCap = globalSaleDetails.SupplyCap;
    int startTime = globalSaleDetails.StartTime;
    int endTime = globalSaleDetails.EndTime;
}

6. Fetching Token Metadata to Display Items to Users

We’ll use the Indexer API to retrieve token supplies for the specified token contract address. Be sure to use the address of the ERC1155 contract, not the sales contract.

public async Task UpdateTokenSuppliesAsync()
{
    Dictionary<BigInteger, TokenSupply> tokenSupplies = new Dictionary<BigInteger, TokenSupply>();
    GetTokenSuppliesArgs supplyArgs = new GetTokenSuppliesArgs(_tokenContractAddress, true);
    GetTokenSuppliesReturn suppliesReturn = await Indexer.GetTokenSupplies((int) _chain, supplyArgs);
 
    foreach (int tokenId in _itemsForSale)
    {
        TokenSupply supply = Array.Find(suppliesReturn.tokenIDs, t => t.tokenID == tokenId);
        if (supply == null)
            continue;
 
        tokenSupplies.Add(supply.tokenID, supply);
    }
}

For example, you can use the supply.tokenMetadata.image variable from the token supplies mentioned above to display your items to the user.

[SerializeField] private Image _image;
 
public async void RenderTokenImage(TokenSupply supply)
{
    _image.sprite = await AssetHandler.GetSpriteAsync(supply.tokenMetadata.image);
}

7. Purchase an Item from the Store

This will call the mint function from the Sales Contract. By specifying the user’s wallet address as the to parameter, the contract will mint the item to that user. You can use the ERC1155Sale.cs class to create a CallContractFunction reference, which allows you to send a transaction to your sales contract using the user's wallet.

class ERC1155SaleState;
 
public async Task<bool> PurchaseAsync(BigInteger tokenId, int amount)
{
    string to = _wallet.GetWalletAddress();
    byte[] defaultProof = Array.Empty<byte>();
 
    CallContractFunction contractCall = _saleContract.Mint(to, new[] {tokenId},
    new[] {new BigInteger(amount)}, null, PaymentToken, new BigInteger(1), defaultProof);
 
    Transaction[] transactions = new Transaction[] { new RawTransaction(contractCall) };
    TransactionReturn result = await _wallet.SendTransaction(_chain, transactions);
    return result is SuccessfulTransactionReturn;
}

When the user clicks the purchase button in the game UI, we call and await the PurchaseAsync function from the sale state class. If the purchase is successful, we show a notification and update the UI. If it fails, we display a QR code for the user to add more funds to their wallet.

class GameWindowUI;
 
private ERC1155SaleState _saleState;
 
public async void OnPurchaseClicked(BigInteger tokenId, int amount)
{
    bool success = await _saleState.PurchaseAsync(tokenId, amount);
    if (!success) {
        OpenQrCodeView();
        return;
    }
 
    ShowNotification("Purchase succeeded.");
    RenderState();
}