How can I implement a ‘restore purchase’ feature for in-app purchases in my mobile game using Defold?

Implementing ‘Restore Purchase’ in Defold

To implement a ‘restore purchase’ feature in your mobile game using Defold, particularly for iOS and Android, you need to follow several key steps. Below is a technical guide to integrating this functionality:

Step 1: Setup Store Services

• iOS with StoreKit: Utilize StoreKit for managing in-app purchases. Ensure you include the required StoreKit framework in your project settings.
• Android with Google Play: Set up Google Play Billing, ensuring your app is configured with the necessary permissions and services in your Android manifest.

Step 2: Create the Restore Callback

With the purchase systems initialized, you’ll need a callback function to handle requests to restore previous transactions. This function will vary slightly between iOS and Android:

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-- Example wrapper to request restoration eequests 
function restore_purchases()
  if system.get_sys_info().system_name == "iOS" then
    -- Call restore function for iOS
    lua_bridge.call("restorePurchases")
  elseif system.get_sys_info().system_name == "Android" then
    -- Call restore function for Android
    lua_bridge.call("restoreTransactions")
  end
end

Step 3: Handle Purchase Restorations

When the restore request is fulfilled, implement logic to handle the successful retrieval of previous purchases.

function handle_restore_response(payment_data)
  for _, product in pairs(payment_data) do
    -- Check each product and restore it accordingly
    if product.state == "restored" then
      manage_restored_purchase(product)
    end
  end
end

Step 4: User Interface for Restore

Provide users with the ability to restore purchases through a button in your game’s UI.

gui.pick_node(self.restore_button_node, action.x, action.y)

Ensure your UI clearly communicates the purpose of the restore function.

Step 5: Testing

Finally, it is crucial to test the restore functionality thoroughly on both iOS and Android platforms. Use sandbox environments and real device testing to confirm that the process aligns with platform guidelines and executes without errors.

Considerations

• Maintain user data across sessions and restorations to ensure a seamless user experience.
• Adhere to both Apple’s and Google’s best practices and precisely follow the StoreKit and Google Play Billing documentation.