1、首先苹果IAP把每次购买抽象成了一个事务（SKPaymentTransaction），

- (void)productsRequest:(SKProductsRequest *)request didReceiveResponse:(SKProductsResponse *)response；
每次在上述方法中收到反馈信息之后添加的[[SKPaymentQueue defaultQueue] addPayment:payment];
就相当于在事务管理中添加了一个事务，只有事务被正常结束（finishTransaction:）该次支付行为才算完成。
即使一次支付中途被中断，这次事务也并没有丢失。假设支付没有完成App就退出了（比如突然崩溃了），那么当下次App重启之后（调用了addTransactionObserver:），之前被中断的事务会接着进行。
这个的缺点就是中间等待重启的时间可能会很长，影响用户体验。

2、在购买成功后的客户端二次验证。

每次购买成功之后都会把encodeStr存到本地，验证成功再进行删除。以后每次打开应用或打开充值会先查看是否有未完成的验证

//交易结果

• (void)paymentQueue:(SKPaymentQueue *)queue updatedTransactions:(NSArray *)transactions{
  NSLog(@"5.交易结果");
  for (SKPaymentTransaction *transaction in transactions){
  switch (transaction.transactionState){
  case SKPaymentTransactionStatePurchased:{//交易完成
  NSLog(@"交易完成");
  [self completeTransaction:transaction];
  } break;
  case SKPaymentTransactionStateFailed://交易失败
  { [self failedTransaction:transaction];
  NSLog(@"-----交易失败 --------");
  [SVProgressHUD dismiss];
  UIAlertView *alerView2 = [[UIAlertView alloc] initWithTitle:@"提示"
  message:@"购买失败，请重新尝试购买"
  delegate:nil cancelButtonTitle:NSLocalizedString(@"关闭",nil) otherButtonTitles:nil];
  [alerView2 show];

      }break;  
      case SKPaymentTransactionStateRestored://已经购买过该商品  
          \[self restoreTransaction:transaction\];  
          NSLog(@"-----已经购买过该商品 --------");  
      case SKPaymentTransactionStatePurchasing:      //商品添加进列表  
          NSLog(@"-----商品添加进列表 --------");  
          break;  
      default:  
          break;  
  }  

  }
  }

• (void)completeTransaction: (SKPaymentTransaction *)transaction{
  NSString * productIdentifier = transaction.payment.productIdentifier;
  if ([productIdentifier length] > 0) {
  [SVProgressHUD dismiss];
  //添加IAPModel到本地
  //获取验证凭证
  NSURL *receiptURL = [[NSBundle mainBundle] appStoreReceiptURL];
  //从沙盒中获取购买凭证
  NSData *receiptData = [NSData dataWithContentsOfURL:receiptURL];
  //进行Base64加密
  NSString *encodeStr = [receiptData base64EncodedStringWithOptions:NSDataBase64EncodingEndLineWithLineFeed];
  WekeIAPModel *model = [[WekeIAPModel alloc]initWithReceiptStr:encodeStr user_id:[AppSingle sharedAppSingle].user_id];
  [[AppSingle sharedAppSingle].IAPArray addObject:model];
  [SaveCachesFile saveDataList:[AppSingle sharedAppSingle].IAPArray fileName:WekeIAP];
  [self verifyPruchaseWithEncodeStr:encodeStr];
  [[SKPaymentQueue defaultQueue] finishTransaction: transaction];
  }else{
  [SVProgressHUD dismiss];
  UIAlertView *alerView2 = [[UIAlertView alloc] initWithTitle:@"提示"
  message:@"购买失败，未能连接到苹果服务器"
  delegate:nil cancelButtonTitle:NSLocalizedString(@"关闭",nil) otherButtonTitles:nil];
  [alerView2 show];
  }
  }
  //验证购买凭证

• (void)verifyPruchaseWithEncodeStr :(NSString *)encodeStr{
  //验证URL POST请求
  NSURL *url = [NSURL URLWithString:Buy_Verify_Receipt_Url];
  NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:20.0f];
  request.HTTPMethod = @"POST";
  NSString *payload = [NSString stringWithFormat:@"{\"receipt-data\" : \"%@\"}", encodeStr];
  NSData *payloadData = [payload dataUsingEncoding:NSUTF8StringEncoding];
  request.HTTPBody = payloadData;
  // 提交验证请求，并获得官方的验证JSON结果
  NSData *result = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
  // 官方验证结果为空
  if (result == nil) {
  NSLog(@"验证失败");
  }else{
  NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:result options:NSJSONReadingAllowFragments error:nil];
  NSLog(@"线上环境验证结果%@",dict);
  if ([[dict objectForKey:@"status"] integerValue] == 21007) {
  //如果是沙盒环境
  [self verifyPruchaseInSANDBOXWithEncodeStr:encodeStr];
  }else if ([[dict objectForKey:@"status"] integerValue] == 0){
  NSLog(@"线上环境验证成功，进行增加积分等操作");
  //验证成功 删除IAP数组中的该Model
  for (WekeIAPModel *model in self.IAPArray) {
  if ([model.encodeStr isEqualToString:encodeStr]) {
  [[AppSingle sharedAppSingle].IAPArray removeObject:model];
  [self.IAPArray removeObject:model];
  [SaveCachesFile saveDataList:[AppSingle sharedAppSingle].IAPArray fileName:WekeIAP];
  }
  }
  [self postGrede];

  }else{  
      NSLog(@"线上环境验证失败");  
      UIAlertController \*alertCT = \[UIAlertController alertControllerWithTitle:@"提示" message:@"充值验证失败,请重试" preferredStyle:(UIAlertControllerStyleAlert)\];  
      UIAlertAction \*cancel = \[UIAlertAction actionWithTitle:@"取消"style:UIAlertActionStyleCancel handler:^(UIAlertAction \* \_Nonnull action) {  
      }\];  
      UIAlertAction \*care = \[UIAlertAction actionWithTitle:@"重试"style:UIAlertActionStyleDefault handler:^(UIAlertAction \* \_Nonnull action) {  
          \[self verifyPruchaseWithEncodeStr:encodeStr\];  
      }\];  
      \[alertCT addAction:cancel\];  
      \[alertCT addAction:care\];  
      \[self presentViewController:alertCT animated:YES completion:nil\];  
  }  

  }
  }

//在沙盒中验证

• (void)verifyPruchaseInSANDBOXWithEncodeStr:(NSString *)encodeStr{

  //验证URL POST请求
  NSURL *url = [NSURL URLWithString:SANDBOX_VERIFY_RECEIPT_URL];
  NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:20.0f];
  request.HTTPMethod = @"POST";
  NSString *payload = [NSString stringWithFormat:@"{\"receipt-data\" : \"%@\"}", encodeStr];
  NSData *payloadData = [payload dataUsingEncoding:NSUTF8StringEncoding];
  request.HTTPBody = payloadData;
  // 提交验证请求，并获得官方的验证JSON结果
  NSData *result = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
  if (result== nil) {
  NSLog(@"沙盒验证失败");
  UIAlertController *alertCT = [UIAlertController alertControllerWithTitle:@"提示" message:@"充值验证失败,请重试" preferredStyle:(UIAlertControllerStyleAlert)];
  UIAlertAction *cancel = [UIAlertAction actionWithTitle:@"取消"style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
  }];
  UIAlertAction *care = [UIAlertAction actionWithTitle:@"重试"style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
  [self verifyPruchaseInSANDBOXWithEncodeStr:encodeStr];
  }];
  [alertCT addAction:cancel];
  [alertCT addAction:care];
  [self presentViewController:alertCT animated:YES completion:nil];
  }else{
  NSLog(@"沙盒验证成功");
  [self postGrede];
  //验证成功 删除IAP数组中的该Model
  for (WekeIAPModel *model in self.IAPArray) {
  if ([model.encodeStr isEqualToString:encodeStr]) {
  [[AppSingle sharedAppSingle].IAPArray removeObject:model];
  [self.IAPArray removeObject:model];
  [SaveCachesFile saveDataList:[AppSingle sharedAppSingle].IAPArray fileName:WekeIAP];
  }
  }

  }
  }