The error state is one of the five UI states. It is pretty important in regards to the user’s experience and satisfaction. If you don’t handle errors probably, they can quickly become the main reason why users lose control of the app, and as a consequence, lead to a reduction in retention or even deletion of the app. 

Error handling is more important when you work with dependencies, especially when working with a library like StoreKit. In general, StoreKit is a black-box in which anything can happen. In this short article, we will explore how to handle failed transactions and give feedback to the user with appropriate error messages.