silverstripe - 在 SilverStripe 中链接/取消链接多对多记录后更新字段

Question

我创建了一个 Customer DataObject通过扩展 Member . Customer有一个 many_many与 Package 的数据关系DataObject .

我想增加/减少 Credits Customer 中的字段DataObject当一个 Package通过基于 Limit 的 CMS 链接/取消链接Package 中的字段 table 。

客户

class Customer extends Member {

    private static $db = array(
        'Gender' => 'Varchar(2)',
        'DateOfBirth' => 'Date',
        'Featured' => 'Boolean',
        'Credits' => 'Int'
    );

    private static $many_many = array(
        'Packages' => 'Package'
    );

    public function getCMSFields() {

        $fields = new FieldList();

        $config = GridFieldConfig_RelationEditor::create();
        $config->removeComponentsByType('GridFieldAddNewButton');

        $packageField = new GridField(
            'Packages',
            'Package',
            $this->Packages(),
            $config
        );

        $fields->addFieldToTab('Root.Package', $packageField); 

        Session::set('SingleID', $this->ID);

        $this->extend('updateCMSFields', $fields);

        return $fields;
    }
}

包

class Package extends DataObject {

    private static $db = array(
        'Title' => 'Varchar(255)',
        'Limit' => 'Int'
    );

    private static $belongs_many_many = array(
        'Customers' => 'Customer'
    );

}

Answer 1

当您创建或删除多对多关系时，只有一条记录在您的数据库中被修改 - 表中的一条记录连接关系双方的元素。因此，关系所基于的对象都不会更新。这就是为什么这样的方法:onBeforeWrite , onAfterWrite , onBeforeDelete和 onAfterDelete根本不会被调用，你不能用它们来检测这种变化。

然而，Silverstripe 提供类 ManyManyList它负责与多对多关系相关的所有操作。有两种您感兴趣的方法:添加和删除。您可以覆盖它们并采取内部行动来做您需要的事情。无论对象类型是什么，这些方法显然都会在每个链接或取消链接操作上调用，因此您应该对您特别感兴趣的类进行一些过滤。

覆盖 ManyManyList 的正确方法class 是使用 Injector 机制，以免修改 framework 或 cms 文件夹内的任何内容。下面的示例使用 Silverstripe 中成员和组之间的关系，但您可以轻松地根据需要采用它(客户 -> 成员；包 -> 组)。

应用程序.yml

Injector:
    ManyManyList:
        class: ManyManyListExtended

ManyManyListExtended.php

/**
 * When adding or removing elements on a many to many relationship
 * neither side of the relationship is updated (written or deleted).
 * SilverStripe does not provide any built-in actions to get information
 * that such event occurs. This is why this class is created.
 *
 * When it is uses together with SilverStripe Injector mechanism it can provide
 * additional actions to run on many-to-many relations (see: class ManyManyList).
 */
class ManyManyListExtended extends ManyManyList {

    /**
     * Overwritten method for adding new element to many-to-many relationship.
     *
     * This is called for all many-to-many relationships combinations.
     * 'joinTable' field is used to make actions on specific relation only.
     *
     * @param mixed $item
     * @param null $extraFields
     * @throws Exception
     */
    public function add($item, $extraFields = null) {
        parent::add($item, $extraFields);

        if ($this->isGroupMembershipChange()) {
            $memberID = $this->getMembershipID($item, 'MemberID');
            $groupID = $this->getMembershipID($item, 'GroupID');
            SS_Log::log("Member ($memberID) added to Group ($groupID)", SS_Log::INFO);
            // ... put some additional actions here
        }
    }

    /**
     * Overwritten method for removing item from many-to-many relationship.
     *
     * This is called for all many-to-many relationships combinations.
     * 'joinTable' field is used to make actions on specific relation only.
     *
     * @param DataObject $item
     */
    public function remove($item) {
        parent::remove($item);

        if ($this->isGroupMembershipChange()) {
            $memberID = $this->getMembershipID($item, 'MemberID');
            $groupID = $this->getMembershipID($item, 'GroupID');
            SS_Log::log("Member ($memberID) removed from Group ($groupID)", SS_Log::INFO);
            // ... put some additional actions here            
        }
    }

    /**
     * Check if relationship is of Group-Member type.
     *
     * @return bool
     */
    private function isGroupMembershipChange() {
        return $this->getJoinTable() === 'Group_Members';
    }

    /**
     * Get the actual ID for many-to-many relationship part - local or foreign key value.
     *
     * This works both ways: make action on a Member being element of a Group OR
     * make action on a Group being part of a Member.
     *
     * @param DataObject|int $item
     * @param string $keyName
     * @return bool|null
     */
    private function getMembershipID($item, $keyName) {
        if ($this->getLocalKey() === $keyName)
            return is_object($item) ? $item->ID : $item;
        if ($this->getForeignKey() === $keyName)
            return $this->getForeignID();
        return false;
    }
}

3dgoo 提供的解决方案也应该可以正常工作，但 IMO 代码会进行更多的“黑客攻击”，这就是为什么它的可维护性要低得多。它需要更多的修改(在两个类中)，如果您想要进行任何额外的链接/取消链接管理，例如添加自定义管理模块或某些表单，则需要成倍增加。