該文檔是蘋果8月5號(hào)發(fā)布的新Technical Note--In-App Purchase Best Practices悯恍，最要描述了iOS 和 OS X 應(yīng)用程序中的IAP的最佳實(shí)踐又固。
以下是推薦給開發(fā)者的IAP最佳實(shí)踐列表。
在應(yīng)用啟動(dòng)時(shí)添加一個(gè)交易隊(duì)列觀察者
應(yīng)用程序調(diào)用StoreKit把觀察者鏈接到payment queue故慈。
[[SKPaymentQueue defaultQueue] addTransactionObserver:your_observer];
在恢復(fù)或者運(yùn)行你的app應(yīng)用時(shí)具练，如果支付隊(duì)列的內(nèi)容發(fā)生了變化，StoreKit則會(huì)自動(dòng)通知你（注冊(cè)的）觀察者 在應(yīng)用啟動(dòng)時(shí)添加觀察者確保它在所有app啟動(dòng)時(shí)都會(huì)存在绰精，這將允許你的應(yīng)用能接收到所有的payment queue提醒。
考慮應(yīng)用程序這樣一個(gè)情況透葛，在向隊(duì)列（如表1）添加支付請(qǐng)求前笨使，應(yīng)用的 DetailViewController 類創(chuàng)建了一個(gè)觀察者。這個(gè)觀察者的存在時(shí)間和 DetailViewController 實(shí)例一樣長(zhǎng)僚害。如果出現(xiàn)中斷情況硫椰，比如網(wǎng)絡(luò)失敗，那么app將不能完成購買流程贡珊，而相關(guān)的交易仍在支付隊(duì)列中最爬。當(dāng)app正常恢復(fù)后门岔，它將沒有觀察者存在爱致，因?yàn)樵趹?yīng)用被發(fā)送至后臺(tái)時(shí)，上述觀察者就已經(jīng)被解除了寒随。因此糠悯，你的應(yīng)用將不會(huì)收到隊(duì)列中的交易通知帮坚。
列表 1.不遵循實(shí)現(xiàn)交易觀察者最佳實(shí)踐：當(dāng)用戶嘗試購買產(chǎn)品時(shí),應(yīng)用為 payment queue 添加觀察者：
@implementation DetailViewController
....
// Called when a customer attempts to purchase a product
- (IBAction)purchase:(id)sender
{
// Register an observer to the payment queue
[[SKPaymentQueue defaultQueue] addTransactionObserver:self];
// Create a payment request
SKMutablePayment *payment = [SKMutablePayment paymentWithProduct:self.product];
// Submit the payment request to the payment queue
[[SKPaymentQueue defaultQueue] addPayment:payment];
}
....
@end
列表 2.遵循注冊(cè)交易觀察者的最佳實(shí)踐
@implementation AppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
// Attach an observer to the payment queue
[[SKPaymentQueue defaultQueue] addTransactionObserver:self];
returnYES;
}
// Called when the application is about to terminate
- (void)applicationWillTerminate:(UIApplication *)application
{
// Remove the observer
[[SKPaymentQueue defaultQueue] removeTransactionObserver:self];
}
....
@end
StoreKit 在app調(diào)用時(shí)從payment queue移除觀察者：
同樣，如果沒有從 payment queue 移除觀察者互艾，StoreKit 將會(huì)試圖通知上述觀察者试和，從而導(dǎo)致應(yīng)用崩潰，好像觀察者已經(jīng)不復(fù)存在了纫普。
在展示應(yīng)用內(nèi)商店UI之前向App Store詢問產(chǎn)品信息
在決定在用戶界面中展示可購買商品之前阅悍，你的應(yīng)用必須首先向App Store發(fā)送一個(gè)產(chǎn)品請(qǐng)求。發(fā)送產(chǎn)品請(qǐng)求可讓你確定產(chǎn)品是否可在App Store中出售昨稼，從而阻止展示不能購買的產(chǎn)品节视。可查看Retrieving Product Information學(xué)習(xí)如何創(chuàng)建一個(gè)產(chǎn)品請(qǐng)求假栓。App Store使用 SKResponse 對(duì)象響應(yīng)產(chǎn)品請(qǐng)求寻行，使用其 products 屬性來更新你的UI，以確保你的用戶只能看到App Store中可供銷售的產(chǎn)品匾荆。
列表 3.不遵循IAP產(chǎn)品展示最佳實(shí)踐：在展示可銷售產(chǎn)品后拌蜘， APP向App Store詢問相關(guān)產(chǎn)品信息。
// App first displays a product for sale, then queries the App Store about it when a customer attempts to purchase it
- (IBAction)purchase:(id)sender
{
// Create a set for your product identifier
NSSet *productSet = [NSSet setWithObject:@"your_product_identifier"];
// Create a product request object and initialize it with the above set
SKProductsRequest *request = [[SKProductsRequest alloc] initWithProductIdentifiers:productSet];
request.delegate = self;
// Send the request to the App Store
[request start];
}
// Get the App Store's response
- (void)productsRequest:(SKProductsRequest *)request didReceiveResponse:(SKProductsResponse *)response
{
// No purchase will take place if there are no products available for sale.
// As a result, StoreKit won't prompt your customer to authenticate their purchase.
if([response.products count] > 0)
{
SKProduct *product = (SKProduct *)[response.products objectAtIndex:0];
// The product is available, let's submit a payment request to the queue
SKMutablePayment *payment = [SKMutablePayment paymentWithProduct:product];
[[SKPaymentQueue defaultQueue] addPayment:payment];
}
}
列表 4. 遵循IAP產(chǎn)品展示最佳實(shí)踐
-(void)fetchProductInformationForIds:(NSArray *)productIds
{
// Create a set for your product identifier
NSSet *mySet = [NSSet setWithObject:your_product_identifier];
// Create a product request object and initialize it with the above set
SKProductsRequest *request = [[SKProductsRequest alloc] initWithProductIdentifiers:mySet];
request.delegate = self;
// Send the request to the App Store
[request start];
}
//Get the App Store's response
- (void)productsRequest:(SKProductsRequest *)request didReceiveResponse:(SKProductsResponse *)response
{
if([response.products count] > 0)
{
// Use availableProducts to populate your UI
NSArray *availableProducts = response.products;
}
}
為restoring products提供一個(gè)UI
如果你的應(yīng)用出售 non-consumable牙丽、auto-renewable subscription 或者 non-renewing subscription產(chǎn)品简卧，那你必須提供一個(gè)允許恢復(fù)它們的UI∈Ｔ溃可以查看Differences Between Product Types和Restoring Purchased Products獲得更多信息贞滨。
處理交易
調(diào)用 StoreKit 為 payment queue 添加支付請(qǐng)求：
[[SKPaymentQueue defaultQueue] addPayment:your_payment];
隊(duì)列創(chuàng)建交易對(duì)象來處理這個(gè)請(qǐng)求。當(dāng)交易狀態(tài)改變時(shí)拍棕，StoreKit通過調(diào)用 paymentQueue: updatedTransactions: 來通知你的觀察者晓铆。
In-App Purchase Programming Guide> Delivering Products> Table 4-1 Transaction statuses and corresponding actions列出了每個(gè)交易可能存在的4種交易狀態(tài)。要確保觀察者的 paymentQueue: updatedTransactions: 可以在任何時(shí)間響應(yīng)這些狀態(tài)绰播。如果IAP產(chǎn)品是由蘋果托管的骄噪，那么需在在觀察者上實(shí)現(xiàn) paymentQueue:updatedDownloads: 方法。
提供付費(fèi)內(nèi)容
當(dāng)收到一個(gè)狀態(tài)是 SKPaymentTransactionStatePurchased 或者 SKPaymentTransactionStateRestored 的交易時(shí)蠢箩，應(yīng)用程序?qū)?huì)向用戶交付內(nèi)容或者解鎖app的功能链蕊。這些狀態(tài)表明已經(jīng)接收到可售產(chǎn)品的付款。用戶也希望應(yīng)用能提供付費(fèi)內(nèi)容谬泌。
如果你的購買產(chǎn)品包括App Store托管內(nèi)容滔韵，要確保調(diào)用 SKPaymentQueue's startDownloads: 下載內(nèi)容≌剖担可查看Unlocking App Functionality和Delivering Associated Content獲得更多信息陪蜻。
完成交付
交易將會(huì)保存在支付隊(duì)列中直到它們被移除。每次啟動(dòng)應(yīng)用或者從后臺(tái)恢復(fù)時(shí)贱鼻，StoreKit將會(huì)調(diào)用觀察者的 paymentQueue: updatedTransactions: 直到它們被移除宴卖。大意是你的用戶可能反復(fù)請(qǐng)求驗(yàn)證它們的購買滋将，或者被阻止購買你的產(chǎn)品。
調(diào)用 finishTransaction: 從隊(duì)列中移除交易症昏。完成的交易是不可恢復(fù)的随闽，因此你務(wù)必提供內(nèi)容，下載所有蘋果托管的產(chǎn)品內(nèi)容肝谭，或者在完成交易前完成你的購買流程掘宪。查看Finishing the Transaction獲得更多信息。
測(cè)試IAP的實(shí)現(xiàn)
要確保在把應(yīng)用提交審核之前徹底測(cè)試IAP的實(shí)現(xiàn)分苇√硭撸可在Suggested Testing Steps查看多測(cè)試場(chǎng)景，在Frequently Asked Questions查看各種疑難解答医寿。
參考：
In-App Purchase Programming Guide
Adding In-App Purchase to your iOS and OS X Applications
WWDC 2012: Selling Products with Store Kit
WWDC 2012: Managing Subscriptions with In-App Purchase
WWDC 2013: Using Store Kit for In-App Purchases
WWDC 2014: Optimizing In-App Purchases
