// 系统大于等于7.0

　　 if ([UIDevice currentDevice].systemVersion.floatValue >= 7.0)
        {
            url = [NSURL URLWithString:@"itms-apps://itunes.apple.com/app/id88888888"];
        }
        else
        {
            url = [NSURL URLWithString:@"itms-apps://ax.itunes.apple.com/WebObjects/MZStore.woa/wa/viewContentsUserReviews?type=Purple+Software&id=88888888"];
        }

上面的88888888对应于要评价的产品在苹果商店中链接中的产品id。