MICROSOFT_PRESS_EBOOK_PROGRAMMING_WINDOWS_8_APPS_WITH_HTML_CSS_AND_JAVASCRIPT_PDF

If you’re using a custom commerce engine, the app will use its own services to retrieve the necessary
product information and handle all the UI and license management for a transaction—the Store API will
not play any role here. If the products are handled through the Store, on the other hand, the
ListingInformation.productListings collection supplies localized product details and the
CurrentApp.requestProductPurchaseAsync method handles the transaction, including the UI. This
section focuses on these APIs.
As noted before, in-app purchases can have expiration dates, after which time the user needs to
repurchase the product to continue its use. This is appropriate for subscriptions or rentals where the
user was fully aware at the time of purchase that the product would eventually expire. In general, you
should always make it clear if a product purchase will expire. Don’t surprise the user or the user will
likely surprise you with a less than favorable review in the Store!
In-app purchases are demonstrated in Scenario 2 of the sample we’ve been using. In this case, the
CurrentAppSimulator is initialized with data/in-app-purchase.xml, which defines two products
(prosaically named Product 1 and Product 2), the first of which has an active license and the second of
which is inactive. When you switch to this scenario (js/in-app-purchase.js), the sample loads the app’s
ListingInformation, retrieves the product details from the productListings collection, and then
displays those options (as shown in Figure 17-5):
currentApp.loadListingInformationAsync().done(
function (listing) {
var product1 = listing.productListings.lookup("product1");
var product2 = listing.productListings.lookup("product2");
document.getElementById("product1SellMessage").innerText =
"You can buy " + product1.name + " for: " + product1.formattedPrice + ".";
document.getElementById("product2SellMessage").innerText =
"You can buy " + product2.name + " for: " + product2.formattedPrice + ".";
});
FIGURE 17-5 Scenario 2 of the Trial apps and in-app purchases sample (cropped); product information obtained
from the Store is displayed in blue text (circled here in red).
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