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https://github.com/silverstripe/silverstripe-framework
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87 lines
2.3 KiB
Markdown
87 lines
2.3 KiB
Markdown
---
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title: Dynamic Default Fields
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summary: Learn how to add default values to your models
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---
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# Default Values and Records
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## Static Default Values
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The [DataObject::$defaults](api:SilverStripe\ORM\DataObject::$defaults) array allows you to specify simple static values to be the default values when a record is created.
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A simple example is if you have a dog and by default its bark is "Woof":
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```php
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use SilverStripe\ORM\DataObject;
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class Dog extends DataObject
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{
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private static $db = [
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'Bark' => 'Varchar(10)',
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];
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private static $defaults = [
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'Bark' => 'Woof',
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];
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}
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```
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## Dynamic Default Values
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In many situations default values need to be dynamically calculated. In order to do this, the
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[DataObject::populateDefaults()](api:SilverStripe\ORM\DataObject::populateDefaults()) method will need to be overloaded.
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This method is called whenever a new record is instantiated, and you must be sure to call the method on the parent
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object!
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A simple example is to set a field to the current date and time:
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```php
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/**
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* Sets the Date field to the current date.
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*/
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public function populateDefaults()
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{
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$this->Date = date('Y-m-d');
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parent::populateDefaults();
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}
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```
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It's also possible to get the data from any other source, or another object, just by using the usual data retrieval
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methods. For example:
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```php
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/**
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* This method combines the Title of the parent object with the Title of this
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* object in the FullTitle field.
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*/
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public function populateDefaults()
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{
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if($parent = $this->Parent()) {
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$this->FullTitle = $parent->Title . ': ' . $this->Title;
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} else {
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$this->FullTitle = $this->Title;
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}
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parent::populateDefaults();
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}
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```
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## Static Default Records
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The [DataObject::$default_records](api:SilverStripe\ORM\DataObject::$default_records) array allows you to specify default records created on dev/build.
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A simple example of this is having a region model and wanting a list of regions created when the site is built:
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```php
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use SilverStripe\ORM\DataObject;
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class Region extends DataObject
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{
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private static $db = [
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'Title' => 'Varchar(45)',
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];
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private static $default_records = [
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['Title' => 'Auckland'],
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['Title' => 'Coromandel'],
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['Title' => 'Waikato'],
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];
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}
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```
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