微信sign签名生成

-(NSString *)createMD5SingForPayWithAppID:(NSString *)appid_key partnerid:(NSString *)partnerid_key prepayid:(NSString *)prepayid_key package:(NSString *)package_key noncestr:(NSString *)noncestr_key timestamp:(UInt32)timestamp_key{

NSMutableDictionary *signParams = [NSMutableDictionary dictionary];
[signParams setObject:appid_key forKey:@"appid"];//微信appid 例如wxfb132134e5342
[signParams setObject:noncestr_key forKey:@"noncestr"];//随机字符串
[signParams setObject:package_key forKey:@"package"];//扩展字段  参数为 Sign=WXPay
[signParams setObject:partnerid_key forKey:@"partnerid"];//商户账号
[signParams setObject:prepayid_key forKey:@"prepayid"];//此处为统一下单接口返回的预支付订单号
[signParams setObject:[NSString stringWithFormat:@"%u",timestamp_key] forKey:@"timestamp"];//时间戳

NSMutableString *contentString  =[NSMutableString string];
NSArray *keys = [signParams allKeys];
//按字母顺序排序
NSArray *sortedArray = [keys sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
    return [obj1 compare:obj2 options:NSNumericSearch];
}];
//拼接字符串
for (NSString *categoryId in sortedArray) {
    if (   ![[signParams objectForKey:categoryId] isEqualToString:@""]
        && ![[signParams objectForKey:categoryId] isEqualToString:@"sign"]
        && ![[signParams objectForKey:categoryId] isEqualToString:@"key"]
        )
    {
        [contentString appendFormat:@"%@=%@&", categoryId, [signParams objectForKey:categoryId]];
    }
}
//添加商户密钥key字段  API 密钥
[contentString appendFormat:@"key=%@", @"BlH3IzF2v3WmZsC1IIowcrjnud3V8wBt"];
NSString *result = [self MD5ForLower32Bate:contentString];//md5加密
return result;

}