iPhone - How to retrieve duration for auto-renewable subscription for in app purchases

I'm looking at setting up In App Purchases f开发者_运维百科or an iPhone app. I'm planning on using the new auto-renewable subscription type. However, I want to offer multiple durations for a particular subscription, but can't see how I can retrieve the duration from the SKProduct that is returned in the SKProductsResponse.products array.

The SKProduct object has price, localizedTitle and localizedDescription. However, if you set up a subscription family with multiple durations the title/description are set once for the family so you cannot include the duration, and the docs explicitly say don't include the duration in the title/description. However, can't see any other field where I can retrieve the duration for displaying in my custom in app store. Either I'm missing something or it isn't going to be available until 4.3?

Pointers greatly appreciated!

You need to have some mapping product_id => length somewhere, either in your app or retrived from your app's backend.

You can use a specific productIdentifier for each duration (in the code below the productIdentifier for a 1 month subscription is "com.domainname.myapp.sub1month" and for a 7 day duration it is "com.domainname.myapp.sub7day") and search for that in the paymentQueue:

-(void) paymentQueue:(SKPaymentQueue *)queue updatedTransactions:(NSArray *)transactions{
   for(SKPaymentTransaction *transaction in transactions){
     switch (transaction.transactionState){
        case SKPaymentTransactionStatePurchasing:
            break;
        case SKPaymentTransactionStatePurchased:
            if([transaction.payment.productIdentifier isEqualToString:@"com.domainname.myapp.sub1month"]{
                newSubscriptionEndDate=[transaction.transactionDate timeIntervalSinceReferenceDate]+3600*24*31;
            }
            if([transaction.payment.productIdentifier isEqualToString:@"com.domainname.myapp.sub7day"]  ){
                newSubscriptionEndDate=[transaction.transactionDate timeIntervalSinceReferenceDate]+3600*24*7;
            }
            [[SKPaymentQueue defaultQueue] finishTransaction: transaction];
            break;

iOS 11.2 brings the subscriptionDuration property to SKProduct. I don't think there is a fallback for older iOS though.

https://developer.apple.com/documentation/storekit/skproduct/2936884-subscriptionperiod