在模型Kohana的ORM自定義方法

Question

我有這兩種模式：

 
class Model_user extends ORM { 
    protected $_has_many = array('credits', array('model'=>'credit', 'foreign_key'=>'user')); 
} 

class Model_credit extends ORM { 
    protected $_belongs_to = array('user', array('model'=>'user', 'foreign_key'=>'user')); 
    protected $_tb = 'credits'; 
    protected $_pk = 'id'; 
    // method to be implemented 
    public function total() { 
     return $total_credits_available; 
    } 
} 

// accessing the 'total' method 
$user = ORM::factory('user', 1); 
$total_credits = $user->credits->total(); 

的事情是如何實現「總」方法，它的確是這樣的：

 
return DB::select(array(DB::expr('SUM(qty * sign)'), 'total')) 
    ->from($this->_tb) 
    ->where('user', '=', $user_id) 
    ->execute() 
    ->total; 

的方法計算用戶的學分（可以是+學分和 - 學分）並返回可用學分總數。只要我使用ORM :: factory方法創建用戶對象，我想以這種方式實現'total'方法，它使用加載的資源而不是運行新的查詢（我寫了上面的查詢來演示業務邏輯）。

有什麼建議嗎？ :)

Answer 1

<?php 
class Model_user extends ORM { 

     protected static $_totals = array(); 

     protected $_has_many = array('credits', array('model'=>'credit', 'foreign_key'=>'user')); 

     public function total() 
     { 
      $total = Arr::get(Model_User::$_totals, $this->id, FALSE); 

      if ($total !== FALSE) 
       return $total; 

      return Model_User::$_totals[$this->id] = $this->credits 
       ->select(array(DB::expr('SUM(qty * sign)'), 'total')) 
       ->find() 
       ->total; 
     } 
    }