CakePHP-HABTM:编辑一个项目会导致HABTM行被重新创建,并破坏额外的数据

我在CakePHP的HABTM关系有问题。

我有两个这样的模型: Department HABTM Location . 一家大公司有许多大楼,每栋大楼提供的服务数量有限。每个建筑也有自己的网页,因此除了HABTM关系本身之外,每个HABTM行也有一个 url

我将模型设置为:

<?php
class Location extends AppModel {
    var $name = 'Location';

    var $hasAndBelongsToMany = array(
        'Department' => array(
            'with' => 'DepartmentsLocation',
            'unique' => true
        )
    );
}
?>


<?php
class Department extends AppModel {
    var $name = 'Department';

    var $hasAndBelongsToMany = array(
        'Location' => array(
            'with' => 'DepartmentsLocation',
            'unique' => true
        )
    );
}
?>

<?php
class DepartmentsLocation extends AppModel {
    var $name = 'DepartmentsLocation';

    var $belongsTo = array(
        'Department',
        'Location'
    );    


    // I'm pretty sure this method is unrelated. It's not being called when this error
    // occurs. Its purpose is to prevent having two HABTM rows with the same location
    // and department.
    function beforeSave() {

        // kill any existing rows with same associations
        $this->log(__FILE__ . ": killing existing HABTM rows", LOG_DEBUG);

        $result = $this->find('all', array("conditions" =>
            array("location_id" => $this->data['DepartmentsLocation']['location_id'],
                  "department_id" => $this->data['DepartmentsLocation']['department_id'])));


        foreach($result as $row) { 
            $this->delete($row['DepartmentsLocation']['id']);
        }

        return true;
    }
}
?>

控制器完全没有意思。

问题是: 如果我编辑一个 位置 ,所有 DepartmentsLocation 位置

我想知道两件事:

还有,用一种不那么专业、更爱发牢骚的语气:为什么会发生这种情况?在我看来很奇怪,通过Cake编辑字段会带来这么多麻烦,当我可以轻松地通过phpMyAdmin时,编辑 位置 说出你的名字,就能得到我所期望的结果。当我只是编辑一行上的字段时,为什么CakePHP会接触HABTM数据?它甚至不是外键!