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Data Types and Casting

Each model in a SilverStripe 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 DBField subclass. The class is responsible for telling the ORM about how to store its data in the database and how to format the information coming out of the database, i.e. on a template.

In the Player example, we have four database columns each with a different data type (Int, Varchar).

mysite/code/Player.php

<?php

class Player extends DataObject {

    private static $db = array(
        'PlayerNumber' => 'Int',
        'FirstName' => 'Varchar(255)',
        'LastName' => 'Text',
        'Birthday' => 'Date'
    );
}

Available Types

  • Boolean: A boolean field.
  • Currency: A number with 2 decimal points of precision, designed to store currency values.
  • Date: A date field
  • Decimal: A decimal number.
  • Enum: An enumeration of a set of strings
  • HTMLText: A variable-length string of up to 2MB, designed to store HTML
  • HTMLVarchar: A variable-length string of up to 255 characters, designed to store HTML
  • Int: An integer field.
  • Percentage: A decimal number between 0 and 1 that represents a percentage.
  • SS_Datetime: A date / time field
  • Text: A variable-length string of up to 2MB, designed to store raw text
  • Time: A time field
  • Varchar: A variable-length string of up to 255 characters, designed to store raw text.

You can define your own 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 Varchar object we can control the formatting and it allows us to call methods defined from Varchar as LimitCharacters.

mysite/code/Player.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.

$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

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 DBField class, providing additional helpers. For example, a string can be cast as a 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.

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 DBField comes with its more sophisticated helpers, like showing the time difference to the current date:

DBField::create_field('Date', '1982-01-01')->TimeDiff(); // shows "30 years ago"

Casting ViewableData

Most objects in SilverStripe extend from 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

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 HTMLVarchar/HTMLText and Varchar/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.

You can disable this auto-escaping by using the $MyField.RAW escaping hints, or explicitly request escaping of HTML content via $MyHtmlField.XML.

Overloading

"Getters" and "Setters" are functions that help us save fields to our 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

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