Triggering In App Purchase for iOS with Custom Action

import 'package:in_app_purchase/in_app_purchase.dart'; // Ensure this is imported
import 'dart:async'; // Required for Completer
Future<String> triggetIAP(String productId) async {
  final InAppPurchase _iap = InAppPurchase.instance;
// Attach listener before initiating the purchase
  final Stream<List<PurchaseDetails>> purchaseStream = _iap.purchaseStream;
  final Completer<String> completer = Completer();

  purchaseStream.listen((List<PurchaseDetails> purchaseDetailsList) {
    for (var purchaseDetails in purchaseDetailsList) {
      if (purchaseDetails.productID == productId) {
        print('Purchase Stream Update: ${purchaseDetails.toString()}');

        switch (purchaseDetails.status) {
          case PurchaseStatus.purchased:
            print(
                'Purchase successful for product: ${purchaseDetails
                    .productID}');
            // Acknowledge the purchase
            _iap.completePurchase(purchaseDetails);
            // Complete the purchase
            completer.complete(purchaseDetails.purchaseID ??
                'Purchase completed but ID is null');
            break;
          case PurchaseStatus.pending:
            print('Purchase is pending...');
            // Handle any UI updates needed for pending status, like showing a spinner
            break;
          case PurchaseStatus.error:
            print('Purchase error: ${purchaseDetails.error}');
            completer.complete('Purchase error: ${purchaseDetails.error}');
            break;
          case PurchaseStatus.restored:
            print(
                'Purchase restored for product: ${purchaseDetails.productID}');
            // Handle the restoration if applicable
            break;
          default:
            print('Unhandled purchase status: ${purchaseDetails.status}');
            break;
        }
      }
    }
  });

// Check if the IAP service is available
  final bool available = await _iap.isAvailable();
  if (!available) {
    print('In-app purchases are not available.');
    return 'In-app purchases are not available';
  }
// Query available products
  final ProductDetailsResponse response =
  await _iap.queryProductDetails({productId});
  if (response.notFoundIDs.isNotEmpty) {
    print('Product not found.');
    return 'Product not found';
  }
// Get the product details
  final ProductDetails product = response.productDetails.first;
// Create a purchase param
  final PurchaseParam purchaseParam = PurchaseParam(productDetails: product);
// Initiate the purchase
  await _iap.buyConsumable(purchaseParam: purchaseParam, autoConsume: true);
// Return the result from the completer
  return completer.future;
}