This chapter has shown how your app may obtain data to perform its functions using the REST API, which provides flexible functionality using the standard HTTP idioms (with HTTP verbs such as PUT, GET, UPDATE, and DELETE). It also showed you how to convert this data into information the user can act on, such as product names, descriptions, and images. In particular, this chapter discussed when to present the Apple Pay button to the user (only when Apple Pay is available on the user's device). Finally, this chapter walked you through the process of creating a payment request, which includes specifying payment information, such as the Apple merchant identifier and merchant capabilities, shipping and billing information, and the summary items that include the total price of the order labeled with your company name for easy verification with payment-card statements.
Now that the user is looking at the payment sheet, your app needs to respond effectively to changes in the shipping methods...
