PHP程序的一次重构记录

项目和新需求：

我们有一个PHP写的webmail系统，有一个mail_list.php用于展现用户的邮件列表这个页面支持folderId参数（因为邮件是存在不同的文件夹下的）由于邮件太多所以支持翻页。现在需要在系统里增加标签。细化下来：需要在原有的邮件列表里增加标签列，和支持tagid检索出一个邮件列表（列表里也增加标签列）

代码和新需求
mail_list.php调用GetMailList函数，这个函数传入文件夹ID,页码，页大小，得到HTML TABLE和导航链接
GetMailList用T_Page类得到请求的一页数据再处理为HTML表格
虽然T_Page只支持单表查询，但是在整个系统里还是被广泛使用

因为动T_Page还是有风险的，所以最好继承它，然后让需要多表查询的地方直接实例化子类

---

重构前

/*
功能：查询指定文件夹下的特定页的邮件列表（HTML Table）
*/
function GetMailList($folderId, $pageNo, $pageSize)
{
    global $db_obj, $pageLink, $html; // db_obj是从外部导入使用，后两个似乎要导出去

    $query = " where folderId = $folderId ..."; //省略很多行
    $pageclass = new T_Page;
    $tableName = "mail";
    $condition = $query . "order by tm desc";
    $pageclass->BaseSet($tableName, "id,sender,subject,content,...", $pageNo, $pageSize, $db_obj);
    $pageclass->SetCondition($condition);

    $record = $pageclass->ReadList(); // 查出来的记录集，被放到二维数组里
    $pageLink=$pageclass->Page(); //存放翻页按钮的数组

    $html = "<table>";
    for($ipage=0;$ipage<$pageSize;$ipage++)
    {
        $i=$ipage;

        $id = $record[$i]["id"];
        $sender = $record[$i]["sender"];
        $subject = $record[$i]["subject"];
        $content = $record[$i]["content"];

        $html = $html . "<tr><td><input type=\"checkbox\" value=\"$id\"></td>";
        $html = $html . "<td>$subject</td>";
        ...
    }
    $html = $html . "</table>";
}
/*
功能： 查询"一页"记录,且输出导航链接用于翻页
*/
class T_Page
{
    var $TableName;
    ...

    function BaseSet($TableName, $Fields, $PageNo, $PageSize, $Obj_DB)
    {
        $this->TableName = $TableName;
        ...

        $this->MaxLine = $this->PageSize;
        $this->Offset = $this->PageNo * $this->PageSize;
    }

    function SetCondition($Condition)
    {
        $this->Condition = $Condition;
    }

    function ReadList()
    {
        $SQL = "select count(*) as recordtotal from $this->tableName $this->Condition";
        $result = $this->Obj_DB->simpleQuery($SQL);
        $row = $this->Obj_DB->fetchRow($result, DB_FETCHMODE_ASSOC);
        $this->Total = $row["recordtotal"];

        if($this->Total > 0)
        {
            $SQL = "select $this->Fields fom $this->tableName $this->Condition limit $this->Offset, $this->MaxLine;";
            $result = $this->Obj_DB->simpleQuery($SQL);
            $this->Number = $this->Obj_DB->numRows($result);

            while($row = $this->Obj_DB->fetchRow($result,DB_FETCHMODE_ASSOC))
            {
                $this->Result[]=$row;
            }
            $this->Obj_DB->freeResult($result);
        }
        return($this->Result)
    }

    function Page()
    {
        if($this->PageNo > 0)
            $this->PageLink[0] = "<a ...>上一页</a>";
        else
            $this->PageLink[0] = "<a>上一页</a>";
        ...
        return $this->PageLink;
    }

    // more function
}

---

重构后

class MailPage extends T_Page
{
    function setTotal()
    {
        ...
        $this->Total = $row["recordtotal"];
    }

    function getMailList()
    {
        $Fields = $this->Field . " ,'' as taglist ";
        $SQL.="select $Fields from $this->Table $this->Condition";
        $SQL.=" LIMIT $this->Offset , $this->MaxLine";

        ...
    }

    function addTagList()
    {
　　　　 ...
        $tagList = Array();
        for($i=0; $i < $this->Number; $i++)
        {
            $key = $this->Result[$i]["id"];
            $this->Result[$i]["taglist"] = $tagList[$key];
        }
    }

    //覆盖父类的接口
    function ReadList()
    {
        $this->setTotal();
        $this->getMailList();
        $this->addTagList();
        return $this->Result;
    }
}

class TagPage extends MailPage
{
    function SetCondition($taglist)
    {
        ...
        $this->Condition = sprintf(" where id in (%s) order by tm desc ", $mailList);
    }
}