面试题：Objective-C的StoreKit内购异常处理

Question

在Objective-C的StoreKit内购流程实现中，可能会遇到购买失败、网络异常等多种情况。请详细说明如何针对这些常见异常进行有效的处理，以提供良好的用户体验，并举例说明关键代码实现。

Answer 1

购买失败处理

1. 监听购买结果：通过实现 SKPaymentTransactionObserver 协议的 paymentQueue:updatedTransactions: 方法来监听交易状态。

- (void)paymentQueue:(SKPaymentQueue *)queue updatedTransactions:(NSArray<SKPaymentTransaction *> *)transactions {
    for (SKPaymentTransaction *transaction in transactions) {
        switch (transaction.transactionState) {
            case SKPaymentTransactionStateFailed:
                // 处理购买失败
                if (transaction.error.code == SKErrorPaymentCancelled) {
                    // 用户取消购买
                    NSLog(@"用户取消购买");
                } else {
                    // 其他失败原因
                    NSLog(@"购买失败: %@", transaction.error.localizedDescription);
                }
                // 完成交易
                [[SKPaymentQueue defaultQueue] finishTransaction:transaction];
                break;
            // 其他状态处理
            case SKPaymentTransactionStatePurchased:
            case SKPaymentTransactionStateRestored:
            case SKPaymentTransactionStateDeferred:
                break;
        }
    }
}

2. 向用户提示：根据失败原因弹出友好的提示框，告知用户失败原因，例如使用 UIAlertController。

UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"购买失败" message:@"您的购买操作未能完成，请检查网络或重试。" preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction *okAction = [UIAlertAction actionWithTitle:@"确定" style:UIAlertActionStyleDefault handler:nil];
[alertController addAction:okAction];
[self presentViewController:alertController animated:YES completion:nil];

网络异常处理

1. 请求前检测网络：在发起购买请求前，使用 Reachability 等工具检测网络状态。

Reachability *reachability = [Reachability reachabilityForInternetConnection];
NetworkStatus networkStatus = [reachability currentReachabilityStatus];
if (networkStatus == NotReachable) {
    // 提示用户网络不可用
    UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"网络异常" message:@"当前网络不可用，请检查网络设置。" preferredStyle:UIAlertControllerStyleAlert];
    UIAlertAction *okAction = [UIAlertAction actionWithTitle:@"确定" style:UIAlertActionStyleDefault handler:nil];
    [alertController addAction:okAction];
    [self presentViewController:alertController animated:YES completion:nil];
    return;
}

2. 请求中处理网络变化：在购买过程中，如果网络发生变化，需要处理正在进行的购买请求。可以监听 Reachability 的网络状态变化通知。

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleNetworkChange:) name:kReachabilityChangedNotification object:nil];

- (void)handleNetworkChange:(NSNotification *)notification {
    Reachability *reachability = [notification object];
    NetworkStatus networkStatus = [reachability currentReachabilityStatus];
    if (networkStatus == NotReachable) {
        // 取消正在进行的购买请求
        NSArray<SKPaymentTransaction *> *transactions = [[SKPaymentQueue defaultQueue] transactions];
        for (SKPaymentTransaction *transaction in transactions) {
            [[SKPaymentQueue defaultQueue] cancelTransaction:transaction];
        }
        // 提示用户网络中断
        UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"网络中断" message:@"购买过程中网络中断，请稍后重试。" preferredStyle:UIAlertControllerStyleAlert];
        UIAlertAction *okAction = [UIAlertAction actionWithTitle:@"确定" style:UIAlertActionStyleDefault handler:nil];
        [alertController addAction:okAction];
        [self presentViewController:alertController animated:YES completion:nil];
    }
}