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97 lines
3.0 KiB
Markdown
97 lines
3.0 KiB
Markdown
---
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title: Extending DataObjects
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summary: Modify the data model without using subclasses.
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---
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# Extending DataObjects
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You can add properties and methods to existing [DataObject](api:SilverStripe\ORM\DataObject)s like [Member](api:SilverStripe\Security\Member) without hacking core code or sub
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classing by using [DataExtension](api:SilverStripe\ORM\DataExtension). See the [Extending SilverStripe](../extending) guide for more information on
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[DataExtension](api:SilverStripe\ORM\DataExtension).
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The following documentation outlines some common hooks that the [Extension](api:SilverStripe\Core\Extension) API provides specifically for managing
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data records.
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## onBeforeWrite
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You can customise saving-behavior for each DataObject, e.g. for adding workflow or data customization. The function is
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triggered when calling *write()* to save the object to the database. This includes saving a page in the CMS or altering
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a `ModelAdmin` record.
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Example: Disallow creation of new players if the currently logged-in player is not a team-manager.
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```php
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use SilverStripe\Security\Security;
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use SilverStripe\ORM\DataObject;
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class Player extends DataObject
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{
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private static $has_many = [
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"Teams" => "Team",
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];
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public function onBeforeWrite()
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{
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// check on first write action, aka "database row creation" (ID-property is not set)
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if(!$this->isInDb()) {
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$currentPlayer = Security::getCurrentUser();
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if(!$currentPlayer->IsTeamManager()) {
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user_error('Player-creation not allowed', E_USER_ERROR);
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exit();
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}
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}
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// check on every write action
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if(!$this->record['TeamID']) {
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user_error('Cannot save player without a valid team', E_USER_ERROR);
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exit();
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}
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// CAUTION: You are required to call the parent-function, otherwise
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// SilverStripe will not execute the request.
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parent::onBeforeWrite();
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}
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}
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```
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## onBeforeDelete
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Triggered before executing *delete()* on an existing object.
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Example: Checking for a specific [permission](permissions) to delete this type of object. It checks if a
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member is logged in who belongs to a group containing the permission "PLAYER_DELETE".
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```php
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use SilverStripe\Security\Permission;
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use SilverStripe\Security\Security;
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use SilverStripe\ORM\DataObject;
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class Player extends DataObject
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{
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private static $has_many = [
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"Teams" => "Team"
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];
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public function onBeforeDelete()
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{
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if(!Permission::check('PLAYER_DELETE')) {
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Security::permissionFailure($this);
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exit();
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}
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parent::onBeforeDelete();
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}
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}
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```
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[notice]
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Note: There are no separate methods for *onBeforeCreate* and *onBeforeUpdate*. Please check `$this->isInDb()` to toggle
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these two modes, as shown in the example above.
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[/notice]
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## Related Lessons
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* [Working with data relationships - $has_many](https://www.silverstripe.org/learn/lessons/v4/working-with-data-relationships-has-many-1)
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