Version 6 pre-stable
This version of Silverstripe CMS has not yet been given a stable release. See the release roadmap for more information. Go to documentation for the most recent stable version.

Extending DataObject models

You can add properties and methods to existing DataObject subclasses like Member without hacking core code or subclassing by using an Extension. See the Extending Silverstripe CMS guide for more information.

The following documentation outlines some common hooks that the Extension API provides specifically for managing data records. Note that this is not an exhaustive list - we encourage you to look at the source code to see what other extension hooks are available.

Avoid using the hooks shown here for checking permissions or validating data - there are specific mechanisms for handling those scenarios. See permissions and validation respectively.

onBeforeWrite

You can customise 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 record via code.

Example: Make sure the player has a valid and unique player number for their team when being assigned a new team.

namespace App\Model;

use SilverStripe\ORM\DataObject;

class Player extends DataObject
{
    private static $db = [
        // ...
        'Number' => 'Int',
    ];

    private static $has_one = [
        'Team' => Team::class,
    ];

    protected function onBeforeWrite()
    {
        // Use $this->isInDb() to check if the record is being written to the database for the first time
        if (!$this->isInDb() && $this->Team()->exists()) {
            $this->Number = $this->Team()->getAvailablePlayerNumber();
        }

        // If the player changed teams
        if ($this->isChanged('TeamID') && $this->Team()->exists()) {
            // If the player's number is already used by someone else on this team
            if (in_array($this->Number, $this->Team()->Players()->exclude('ID', $this->ID)->column('Number'))) {
                // Assign a new player number
                $this->Number = $this->Team()->getAvailablePlayerNumber();
            }
        }

        // CAUTION: You are required to call parent::onBeforeWrite(), otherwise
        // SilverStripe will not execute the request.
        parent::onBeforeWrite();
    }
}

onBeforeDelete

Triggered before executing delete() on an existing object. It can be useful if you need to make sure you clean up some other data/files/etc which aren't directly associated with the actual DataObject record.

namespace App\Model;

use SilverStripe\ORM\DataObject;

class Player extends DataObject
{
    // ...

    protected function onBeforeDelete()
    {
        /* Do some cleanup here relevant to your project before deleting the actual database record */

        // CAUTION: You are required to call parent::onBeforeDelete(), otherwise
        // SilverStripe will not execute the request.
        parent::onBeforeDelete();
    }
}

Note: There are no separate methods for onBeforeCreate() and onBeforeUpdate(). Please check $this->isInDb() to toggle these two modes, as shown in the example above.

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