# 实现应用商店

> Implement the IStore interface to add a custom store to Unity In-App Purchasing.

您的应用商店必须实现 IStore 接口；我们将在以下部分详细介绍其方法。

```
using UnityEngine.Purchasing.Extension;

public class MyStore : IStore
{
    private IStoreCallback callback;
    public void Initialize (IStoreCallback callback)
    {
        this.callback = callback;   
    }

    public void RetrieveProducts (System.Collections.ObjectModel.ReadOnlyCollection<UnityEngine.Purchasing.ProductDefinition> products)
    {
        // Fetch product information and invoke callback.OnProductsRetrieved();
    }

    public void Purchase (UnityEngine.Purchasing.ProductDefinition product, string developerPayload)
    {
        // Start the purchase flow and call either callback.OnPurchaseSucceeded() or callback.OnPurchaseFailed()
    }

    public void FinishTransaction (UnityEngine.Purchasing.ProductDefinition product, string transactionId)
    {
        // Perform transaction related housekeeping 
    }
}
```