2.4 KiB
title: Extending DataObjects summary: Modify the data model without using subclasses.
Extending DataObjects
You can add properties and methods to existing [api:DataObject]s like [api:Member] without hacking core code or sub classing by using [api:DataExtension]. See the Extending SilverStripe guide for more information on [api:DataExtension].
The following documentation outlines some common hooks that the [api:Extension] API provides specifically for managing data records.
onBeforeWrite
You can customize saving-behavior for each DataObject, e.g. for adding workflow or data customization. The function is
triggered when calling write() to save the object to the database. This includes saving a page in the CMS or altering
a ModelAdmin record.
Example: Disallow creation of new players if the currently logged-in player is not a team-manager.
:::php
<?php
class Player extends DataObject {
private static $has_many = array(
"Teams"=>"Team"
);
public function onBeforeWrite() {
// check on first write action, aka "database row creation" (ID-property is not set)
if(!$this->isInDb()) {
$currentPlayer = Member::currentUser();
if(!$currentPlayer->IsTeamManager()) {
user_error('Player-creation not allowed', E_USER_ERROR);
exit();
}
}
// check on every write action
if(!$this->record['TeamID']) {
user_error('Cannot save player without a valid team', E_USER_ERROR);
exit();
}
// CAUTION: You are required to call the parent-function, otherwise
// SilverStripe will not execute the request.
parent::onBeforeWrite();
}
}
onBeforeDelete
Triggered before executing delete() on an existing object.
Example: Checking for a specific permission to delete this type of object. It checks if a member is logged in who belongs to a group containing the permission "PLAYER_DELETE".
:::php
<?php
class Player extends DataObject {
private static $has_many = array(
"Teams" => "Team"
);
public function onBeforeDelete() {
if(!Permission::check('PLAYER_DELETE')) {
Security::permissionFailure($this);
exit();
}
parent::onBeforeDelete();
}
}