优惠分为两种类型

@property(nonatomic, readonly) SKProductDiscountType type API_AVAILABLE(ios(12.2), macos(10.14.4), watchos(6.2));

typedef NS_ENUM(NSUInteger, SKProductDiscountType) {
    SKProductDiscountTypeIntroductory, // 推介优惠
    SKProductDiscountTypeSubscription, // 促销优惠
} NS_SWIFT_NAME(SKProductDiscount.Type) API_AVAILABLE(ios(12.2), macos(10.14.4), watchos(6.2));

推介优惠

苹果会根据该苹果ID是否享受推介优惠，会自动下发该优惠信息，享受过的ID获取不到推介优惠信息，沙盒环境可以到后台清除沙盒账号购买记录重新购买测试

@property(nonatomic, readonly, nullable) SKProductDiscount *introductoryPrice API_AVAILABLE(ios(11.2), macos(10.13.2), watchos(6.2));

促销优惠

促销优惠为数组，可以获取到后台配置的促销优惠列表

@property(nonatomic, readonly) NSArray<SKProductDiscount *> *discounts API_AVAILABLE(ios(12.2), macos(10.14.4), watchos(6.2));

以上两种优惠都包含以下三种促销类型

@property(nonatomic, readonly) SKProductDiscountPaymentMode paymentMode API_AVAILABLE(ios(11.2), macos(10.13.2), watchos(6.2));

typedef NS_ENUM(NSUInteger, SKProductDiscountPaymentMode) {
   SKProductDiscountPaymentModePayAsYouGo, // 随用随付
   SKProductDiscountPaymentModePayUpFront, // 提前支付
   SKProductDiscountPaymentModeFreeTrial // 免费试用
} NS_SWIFT_NAME(SKProductDiscount.PaymentMode) API_AVAILABLE(ios(11.2), macos(10.13.2), watchos(6.2));

商品信息上报

SKProductDiscountPaymentModePayAsYouGo 取周期方式区别于其他2种优惠，需特殊处理

+ (NSDictionary *)createProductParams:(SKProduct *) product {
    
    if (!product) return nil;
    
    NSNumberFormatter *nf = [[NSNumberFormatter alloc] init];
    [nf setFormatterBehavior:NSNumberFormatterBehavior10_4];
    [nf setNumberStyle:NSNumberFormatterCurrencyStyle];
    [nf setLocale:product.priceLocale];
    NSNumber *price = product.price;
    NSString *currencyCode = nf.currencyCode;
    NSString *countryCode = @"";
    if (@available(iOS 10.0, *)) {
        countryCode = [nf.locale countryCode];
    }
    NSString *symbol = [nf currencySymbol];
    
    NSMutableDictionary *params = [NSMutableDictionary dictionary];
    [params setObject:product.productIdentifier ?: @"" forKey:@"product_id"];
    [params setObject:price ?: @"" forKey:@"price"];
    [params setObject:countryCode forKey:@"country_code"];
    [params setObject:currencyCode ?: @"" forKey:@"currency_code"];
    [params setObject:symbol ?: @"" forKey:@"symbol"];

    if (@available(iOS 12.2, *)) {
        NSMutableArray *promotions = [NSMutableArray array];

        NSArray <SKProductDiscount *>* discounts = product.discounts;
        for (SKProductDiscount *discount in discounts) {
            [promotions addObject:[self productPromotion:discount]];
        }
        
        // 推介优惠
        SKProductDiscount *introductoryPrice = product.introductoryPrice;
        if (introductoryPrice) {
            [promotions addObject:[self productPromotion:introductoryPrice]];
        }
        
        [params setObject:promotions forKey:@"promotion"];
    }
    
    return params.copy;
}

+(NSDictionary *)productPromotion:(SKProductDiscount *) discount {
    if (@available(iOS 12.2, *)) {
        // 促销价格
        NSDecimalNumber *promotionPrice = discount.price;
        // 促销周期
        NSInteger periods = discount.subscriptionPeriod.unit;
        // 优惠类型
        NSInteger type = discount.type;
        // 促销码
        NSString *code = discount.identifier ?: @"";
        // 促销期数
        NSInteger count = discount.subscriptionPeriod.numberOfUnits;
        if (discount.paymentMode == SKProductDiscountPaymentModePayAsYouGo) {
            count = discount.numberOfPeriods;
        }
        // 促销类型
        NSInteger mode = discount.paymentMode;
        
        NSMutableDictionary *promotion = [NSMutableDictionary dictionary];
        [promotion setObject:promotionPrice forKey:@"promotion_price"];
        [promotion setObject:@(periods) forKey:@"promotion_period"];
        [promotion setObject:@(type) forKey:@"discount_type"];
        [promotion setObject:@(mode) forKey:@"promotion_type"];
        [promotion setObject:code forKey:@"promotion_code"];
        [promotion setObject:@(count) forKey:@"promotion_time"];
        
        return promotion.copy;
    }
    return @{};
}