删除数据对象时删除文件

Question

我有'Resouce‘数据对象，如下所示，附件作为has_one关系。当“资源”对象被删除时，我想删除附件。

但是我得到的是致命错误:调用非对象的成员函数delete()

<?php 
class Resource extends DataObject
{ 
private static $db = array (
    'Name' => 'Varchar(200)',
    'Description' => 'Text',
    'Category' => "Enum('Data, Drafts, Drawings, Reports, Images, Other')",
    'SortOrder' => 'Int'
);

private static $has_one = array (
    'Attachment' => 'File',
    'ResourcePage' => 'ResourcePage'
);


public function onBeforeDelete()
{
    $myAttachment = $this->Attachment();
    $file = DataObject::get_by_id('File', $myAttachment->ID); //we have to make sure it is a Dataobject object      
    $file->delete();
    $file->destroy();       
    return parent::onBeforeDelete();                    
}

}

Answer 1

这里的问题是假设DataObject::get_by_id总是返回一个对象是不正确的。您可以首先检查$file是一个非假值，也可以通过has_one getter执行所有操作，使用：

public function onBeforeDelete() {
    if ($this->Attachment()->exists()) {
        $this->Attachment()->delete();
    }
}