我在谷歌上找了一些关于这个的例子/解决方案，例如Creating Discount Code System (MySQL/php)，但我还没有找到一个好的解决方案。
我的情况是这样的，我有一个平台，用户应该有一个虚拟货币余额，可以用它购买虚拟物品。现在有一个愿望，实现券和折扣。会有不同种类的代码，如一个给50%的折扣购买物品，x数量的额外物品（有或没有最低项目金额），只是一个代码，以获得一些货币，或参考代码，给引荐的东西。
我已经将其实现为Campaign和CampaignType，其中第一个保存Campaign信息，第二个保存action信息。
结构如下：

-- Table structure for table `cake_campaigns`

CREATE TABLE IF NOT EXISTS `cake_campaigns` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `name` varchar(50) CHARACTER SET utf8 NOT NULL,
  `code` varchar(100) COLLATE utf8_bin NOT NULL,
  `type_id` varchar(50) CHARACTER SET utf16 COLLATE utf16_bin NOT NULL DEFAULT '1',
  `value` int(10) unsigned NOT NULL DEFAULT '5' COMMENT 'Percentage or amount',
  `min_amount` bigint(20) unsigned NOT NULL DEFAULT '0',
  `owner_id` bigint(20) unsigned NOT NULL,
  `created` datetime NOT NULL,
  `active` tinyint(1) unsigned NOT NULL DEFAULT '1',
  `single_use` tinyint(1) unsigned NOT NULL DEFAULT '0',
  PRIMARY KEY (`id`),
  UNIQUE KEY `code` (`code`),
  KEY `owner_id` (`owner_id`),
  FULLTEXT KEY `name` (`name`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 COLLATE=utf8_bin AUTO_INCREMENT=4 ;

-- Table structure for table `cake_campaign_types`

CREATE TABLE IF NOT EXISTS `cake_campaign_types` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(50) CHARACTER SET utf8 NOT NULL,
  `unit` varchar(10) CHARACTER SET utf16 NOT NULL DEFAULT '%',
  `multiplier` double(10,8) NOT NULL DEFAULT '0.01000000',
  `type` varchar(50) COLLATE utf8_bin DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `name` (`name`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 COLLATE=utf8_bin AUTO_INCREMENT=7 ;

目前，我的逻辑是，当使用活动时，则根据CampaignType的名称执行操作，例如在购买逻辑中：

if (isset($this->request->data['Purchase']['code'])) {
    $code = $this->request->data['Purchase']['code'];
    $campaign = $this->Campaign->findByCode($code);
    $this->Campaign->id = $campaign['Campaign']['id'];

    // campaign no longer active
    if ($this->Campaign->field('active') == 0) $code = false;

    if ($this->CampaignLog->find('first', array('conditions' => array(
            'user_id' => $this->User->field('id'),
            'campaign_id' => $this->Campaign->field('id'),
            'activated' => 1,
        )))) $code = false; // code has already been used

    unset($this->request->data['Purchase']['code']);
} else $code = false;

// Some purchasing logic here

if ($code) {
    $this->CampaignLog->create();
    $this->CampaignLog->save(array(
            'campaign_id' => $this->Campaign->field('id'),
            'user_id' => $this->User->field('id'),
            'activated' => 1,
            'source' => $this->Session->read('referrer'),
            'earnings' => $earned,
            'created' => strftime('%Y-%m-%d %H:%M:%S'),
        ));

    if ($this->Campaign->field('single_use') == 1) {
        $this->Campaign->saveField("active", 0);
    }

    // Apply code here
}

现在，我的问题是：在应用这些代码时，最好的做法是什么？因为我对使用if-then-else或switch-case来遍历所有可能的代码类型有点反感。但现在，既然有这么多的东西可以不同（例如折扣-以百分比或设定金额表示），那么这似乎是唯一的选择。也许代码的结构/逻辑应该不同？