[in_app_purchase] How to Use Promotional Offers for iOS Subscriptions

[xiaolongwuhpu]

Description:

I'm trying to implement promotional offers for iOS subscriptions using the [in_app_purchase] library. For example: offering the first week for free or providing a discount for the first year.
In my Android project, I've successfully implemented these offers using the following code:

 late PurchaseParam purchaseParam;
    if (Device.isAndroid) {
// Code snippet for implementing promotional offers in Android
// Different promotional offers have different ProductDetails, making it easy to implement them
      purchaseParam = GooglePlayPurchaseParam(productDetails: productDetails, changeSubscriptionParam: null);
    } else if(Device.isIOS) {
      purchaseParam = AppStorePurchaseParam(
        productDetails: productDetails,
        discount: SKPaymentDiscountWrapper(identifier: '', keyIdentifier: '', nonce: '', signature: "", timestamp: DateTime.now().millisecondsSinceEpoch),
      );
    }
    bool paySuccess = await _inAppPurchase.buyNonConsumable(purchaseParam: purchaseParam);

However, I'm unsure about how to achieve the same in iOS. Can someone please provide detailed guidance? I've gone through the documentation here but couldn't grasp it entirely. Do we need our server to generate signatures for this?

Thank you for any assistance you can provide!

if(Device.isIOS) {
      purchaseParam = AppStorePurchaseParam(
        productDetails: productDetails,
        discount: SKPaymentDiscountWrapper(identifier: '', keyIdentifier: '', nonce: '', signature: "", timestamp: DateTime.now().millisecondsSinceEpoch),
      );
    }

Where can I obtain the parameters for this class SKPaymentDiscountWrapper, and how should I construct this object? Are there any alternative approaches to achieve this?

doc: https://developer.apple.com/documentation/storekit/in-app_purchase/original_api_for_in-app_purchase/subscriptions_and_offers/generating_a_signature_for_promotional_offers?language=objc

[huycozy]

Hi @xiaolongwuhpu
The promotional offers request on iOS has been implemented by flutter/plugins#4458 (issue #92231).

It depends on your subscription type to be able to get offers, please check this answer for the detail: #92872 (comment). There is also outlined: you can find discount from SKProductWrapper.discounts or SKPaymentWrapper.paymentDiscount. I check this quickly with package example and see you may get it through SKPaymentTransactionWrapper transaction, for e.g: transaction.payment.paymentDiscount.

https://github.com/flutter/packages/blob/1f208aa26454fb4debdfd1ebed9ee0d918b93c9a/packages/in_app_purchase/in_app_purchase/example/lib/main.dart#L502

Also, this is more of a how-to question than a bug or feature request. I see there is a known issue asking the example for this: #51757. So I would suggest you ask the same there (if my suggest above doesn't work) that may help to raise the issue. I will go ahead and close this in favor of that one. Thanks!

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