6.0 KiB
title: Data Types, Overloading and Casting summary: Documentation on how data is stored going in, coming out of the ORM and how to modify it.
Data Types and Casting
Each model in a SilverStripe [api:DataObject] will handle data at some point. This includes database columns such as
the ones defined in a $db array or simply a method that returns data for the template.
A Data Type is represented in SilverStripe by a [api:DBField] subclass. The class is responsible for telling the ORM about how to store it's data in the database and how to format the information coming out of the database.
In the Player example, we have four database columns each with a different data type (Int, Varchar).
mysite/code/Player.php
:::php
<?php
class Player extends DataObject {
private static $db = array(
'PlayerNumber' => 'Int',
'FirstName' => 'Varchar(255)',
'LastName' => 'Text',
'Birthday' => 'Date'
);
}
Available Types
- [api:Boolean]: A boolean field.
- [api:Currency]: A number with 2 decimal points of precision, designed to store currency values.
- [api:Date]: A date field
- [api:Decimal]: A decimal number.
- [api:Enum]: An enumeration of a set of strings
- [api:HTMLText]: A variable-length string of up to 2MB, designed to store HTML
- [api:HTMLVarchar]: A variable-length string of up to 255 characters, designed to store HTML
- [api:Int]: An integer field.
- [api:Percentage]: A decimal number between 0 and 1 that represents a percentage.
- [api:SS_Datetime]: A date / time field
- [api:Text]: A variable-length string of up to 2MB, designed to store raw text
- [api:Time]: A time field
- [api:Varchar]: A variable-length string of up to 255 characters, designed to store raw text.
You can define your own [api:DBField] instances if required as well. See the API documentation for a list of all the available subclasses.
Formatting Output
The Data Type does more than setup the correct database schema. They can also define methods and formatting helpers for output. You can manually create instances of a Data Type and pass it through to the template.
If this case, we'll create a new method for our Player that returns the full name. By wrapping this in a [api:Varchar]
object we can control the formatting and it allows us to call methods defined from Varchar as LimitCharacters.
mysite/code/Player.php
:::php
<?php
class Player extends DataObject {
..
public function getName() {
return DBField::create_field('Varchar', $this->FirstName . ' '. $this->LastName);
}
}
Then we can refer to a new Name column on our Player instances. In templates we don't need to use the get prefix.
:::php
$player = Player::get()->byId(1);
echo $player->Name;
// returns "Sam Minnée"
echo $player->getName();
// returns "Sam Minnée";
echo $player->getName()->LimitCharacters(2);
// returns "Sa.."
Casting
Rather than manually returning objects from your custom functions. You can use the $casting property.
:::php
<?php
class Player extends DataObject {
private static $casting = array(
"Name" => 'Varchar',
);
public function getName() {
return $this->FirstName . ' '. $this->LastName;
}
}
The properties on any SilverStripe object can be type casted automatically, by transforming its scalar value into an
instance of the [api:DBField] class, providing additional helpers. For example, a string can be cast as a [api:Text]
type, which has a FirstSentence() method to retrieve the first sentence in a longer piece of text.
On the most basic level, the class can be used as simple conversion class from one value to another, e.g. to round a number.
:::php
DBField::create_field('Double', 1.23456)->Round(2); // results in 1.23
Of course that's much more verbose than the equivalent PHP call. The power of [api:DBField] comes with its more sophisticated helpers, like showing the time difference to the current date:
:::php
DBField::create_field('Date', '1982-01-01')->TimeDiff(); // shows "30 years ago"
Casting ViewableData
Most objects in SilverStripe extend from [api:ViewableData], which means they know how to present themselves in a view
context. Through a $casting array, arbitrary properties and getters can be casted:
:::php
<?php
class MyObject extends ViewableData {
private static $casting = array(
'MyDate' => 'Date'
);
public function getMyDate() {
return '1982-01-01';
}
}
$obj = new MyObject;
$obj->getMyDate(); // returns string
$obj->MyDate; // returns string
$obj->obj('MyDate'); // returns object
$obj->obj('MyDate')->InPast(); // returns boolean
Casting HTML Text
The database field types [api:HTMLVarchar]/[api:HTMLText] and [api:Varchar]/[api:Text] are exactly the same in
the database. However, the template engine knows to escape fields without the HTML prefix automatically in templates,
to prevent them from rendering HTML interpreted by browsers. This escaping prevents attacks like CSRF or XSS (see
"security"), which is important if these fields store user-provided data.
Overloading
"Getters" and "Setters" are functions that help us save fields to our [api:DataObject] instances. By default, the
methods getField() and setField() are used to set column data. They save to the protected array, $obj->record.
We can overload the default behavior by making a function called "get<fieldname>" or "set<fieldname>".
The following example will use the result of getStatus instead of the 'Status' database column. We can refer to the
database column using dbObject.
:::php
<?php
class Player extends DataObject {
private static $db = array(
"Status" => "Enum(array('Active', 'Injured', 'Retired'))"
);
public function getStatus() {
return (!$this->obj("Birthday")->InPast()) ? "Unborn" : $this->dbObject('Status')->Value();
}
API Documentation
- [api:DataObject]
- [api:DBField]