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原文出处：https://www.jianshu.com/p/40da3c2730ed

需要监听内购的地方加上(一般初始化的时候)：

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(rechargeResult:) name:kIAPNotification_Recharge object:nil];

注销监听内购的地方加上(一般销毁的时候)：

[[NSNotificationCenter defaultCenter] removeObserver:kIAPNotification_Recharge];

支付：buy 产品ID 需要在苹果开发这后台添加商品ID
回调：处理支付结果 1、_buy_ok 2、_buy_failed

IAP.h

#import <StoreKit/StoreKit.h>

extern NSString *const kIAPNotification_Recharge;
@interface IAP_Delegate : NSObject<SKProductsRequestDelegate, SKPaymentTransactionObserver>

- (id)init;
- (void)dealloc;

- (void)buy:(const char *)product;

- (void)_buy_ok:(SKPaymentTransaction *)transaction;
- (void)_buy_failed:(SKPaymentTransaction *)transaction;
- (void)_buy_restored:(SKPaymentTransaction *)transaction;

@end

IAP.mm

#import "IAP.h" 

NSString *const kIAPNotification_Recharge = @"IAPNotification_Recharge";
@implementation IAP_Delegate

- (id)init
{
    self = [super init];
    if (self) {
        [[SKPaymentQueue defaultQueue] addTransactionObserver:self];
    }
    return self;
}

- (void)dealloc
{
    [[SKPaymentQueue defaultQueue] removeTransactionObserver:self];
    [super dealloc];
}

- (void)buy:(const char *)product
{
    NSSet *set = [NSSet setWithArray:@[[NSString stringWithUTF8String:product]]];
    SKProductsRequest *request = [[SKProductsRequest alloc] initWithProductIdentifiers:set];
    [request setDelegate:self];
    [request start];
}

- (void)_buy_ok:(SKPaymentTransaction *)transaction
{
    NSString *product = transaction.payment.productIdentifier;
    NSString *receipt = nil;
#if __IPHONE_OS_VERSION_MAX_ALLOWED < __IPHONE_7_0
    receipt = [transaction.transactionReceipt base64Encoding];
#else
    NSURL *receiptURL = [[NSBundle mainBundle] appStoreReceiptURL];
    receipt = [[NSData dataWithContentsOfURL:receiptURL] base64EncodedStringWithOptions:0];
#endif
    
    NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:@"0",@"result",product,@"product", receipt, @"receipt",nil];
    [[NSNotificationCenter defaultCenter]postNotificationName:kIAPNotification_Recharge object:self userInfo:dict];
    [[SKPaymentQueue defaultQueue] finishTransaction:transaction];
}

- (void)_buy_failed:(SKPaymentTransaction *)transaction
{
    NSString *product = transaction.payment.productIdentifier;
    if (transaction.error.code == SKErrorPaymentCancelled) {
         NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:@"1",@"result",product,@"product",nil];
         [[NSNotificationCenter defaultCenter]postNotificationName:kIAPNotification_Recharge object:self userInfo:dict];
    } else {
        NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:@"2",@"result",product,@"product",nil];
       [[NSNotificationCenter defaultCenter]postNotificationName:kIAPNotification_Recharge object:self userInfo:dict];
    }
    [[SKPaymentQueue defaultQueue] finishTransaction:transaction];
}

- (void)_buy_restored:(SKPaymentTransaction *)transaction
{
    NSString *product = transaction.payment.productIdentifier;
     NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:@"3",@"result",product,@"product",nil];
    [[NSNotificationCenter defaultCenter]postNotificationName:kIAPNotification_Recharge object:self userInfo:dict];
    [[SKPaymentQueue defaultQueue] finishTransaction:transaction];
}

#pragma mark -
#pragma mark SKProductsRequestDelegate
- (void)productsRequest:(SKProductsRequest *)request didReceiveResponse:(SKProductsResponse *)response
{
    NSLog(@"---------收到产品反馈信息---------");
    NSArray *pids = [response invalidProductIdentifiers];
    NSLog(@"产品Product ID:%@", pids);
    NSLog(@"产品付费数量:%d", (int)[[response products] count]);
    
    if (![[response products] count]) {
        NSString *product = 0;
        
        if ([pids count]) {
            product = (NSString *)[pids objectAtIndex:0];
        }
        NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:@"2",@"result",product,@"product",nil];
        [[NSNotificationCenter defaultCenter]postNotificationName:kIAPNotification_Recharge object:self userInfo:dict];

        return ;
    }
    
    NSLog(@"-------------发送购买请求----------------");
    SKPayment *payment = [SKPayment paymentWithProduct:[[response products] objectAtIndex:0]];
    [[SKPaymentQueue defaultQueue] addPayment:payment];
}

#pragma mark -
#pragma mark SKPaymentTransactionObserver
- (void)paymentQueue:(SKPaymentQueue *)queue updatedTransactions:(NSArray *)transactions
{
    for (SKPaymentTransaction *transaction in transactions)
    {
        switch (transaction.transactionState)
        {
            case SKPaymentTransactionStatePurchasing:
                // do nothing.
                break;
            case SKPaymentTransactionStatePurchased:
                [self _buy_ok:transaction];
                break;
            case SKPaymentTransactionStateFailed:
                [self _buy_failed:transaction];
                break;
            case SKPaymentTransactionStateRestored:
                [self _buy_restored:transaction];
                break;
                
            case SKPaymentTransactionStateDeferred:
                // i don't know...
                break;
        }
    }
}

@end