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https://github.com/silverstripe/silverstripe-framework
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85 lines
2.4 KiB
Markdown
85 lines
2.4 KiB
Markdown
title: Extending DataObjects
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summary: Modify the data model without using subclasses.
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# Extending DataObjects
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You can add properties and methods to existing [api:DataObject]s like [api:Member] without hacking core code or sub
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classing by using [api:DataExtension]. See the [Extending SilverStripe](../extending) guide for more information on
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[api:DataExtension].
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The following documentation outlines some common hooks that the [api:Extension] API provides specifically for managing
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data records.
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## onBeforeWrite
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You can customize 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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<?php
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class Player extends DataObject {
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private static $has_many = array(
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"Teams"=>"Team"
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);
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public function onBeforeWrite() {
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// check on first write action, aka "database row creation" (ID-property is not set)
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if(!$this->isInDb()) {
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$currentPlayer = Member::currentUser();
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if(!$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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## 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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<?php
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class Player extends DataObject {
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private static $has_many = array(
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"Teams" => "Team"
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);
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public function onBeforeDelete() {
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if(!Permission::check('PLAYER_DELETE')) {
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Security::permissionFailure($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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<div class="notice" markdown='1'>
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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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</div>
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