iOS - in-app payments with non-iTunes Store payments

Question

I am wondering what the rules are around using an external payment system (like Braintree) for in-app purchases on iOS. We already run a streaming music service that operates over the web, and we want to develop apps for Android+iOS. It's a subscription service, and we currently run all our payments through Braintree. If at all possible, we'd like to continue to do so.

I'm a little hazy on the exact details of when this is allowed and when it's verboten.

This would allow users to stream full tracks within the app (otherwise all they get are 30-second previews), but it also allows them to use the subscription online and on other platforms. So, would this therefore be an allowable use of a 3rd party payment system by the "law of Apple?"

Answer 1

From the guidelines:

11.1

Apps that unlock or enable additional features or functionality with mechanisms other than the App Store will be rejected

11.2

Apps utilizing a system other than the In-App Purchase API (IAP) to purchase content, functionality, or services in an App will be rejected

https://developer.apple.com/app-store/review/guidelines/