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Datamodel
SilverStripe uses an object-relational model that assumes the following connections:
- Each database-table maps to a PHP class
- Each database-row maps to a PHP object
- Each database-column maps to a property on a PHP object
All data tables in SilverStripe are defined as subclasses of [api:DataObject].
Inheritance is supported in the data model: separate tables will be linked together, the data spread across these tables. The mapping and saving/loading logic is handled by SilverStripe, you don't need to worry about writing SQL most of the time.
Most of the ORM customizations are possible through PHP5 Object
Overloading
handled in the [api:Object]-class.
See database-structure for in-depth information on the database-schema and the "sql queries" topic in case you need to drop down to the bare metal.
Generating the Database Schema
The SilverStripe database-schema is generated automatically by visiting the URL.
http://localhost/dev/build
Querying Data
Every query to data starts with a DataList::create(<class>) or <class>::get()
call. For example, this query would return all of the Member objects:
:::php
$members = Member::get();
The ORM uses a "fluent" syntax, where you specify a query by chaining together
different methods. Two common methods are filter() and sort():
:::php
$members = Member::get()->filter(array(
'FirstName' => 'Sam'
))->sort('Surname');
Those of you who know a bit about SQL might be thinking "it looks like you're querying all members, and then filtering to those with a first name of 'Sam'.
Isn't this very slow?" Is isn't, because the ORM doesn't actually execute the
SQL query until you iterate on the result with a foreach() or <% loop %>.
The ORM is smart enough to generate a single efficient query at the last moment
in time without needing to post process the result set in PHP. In MySQL the
query generated by the ORM may look something like this for the previous query.
:::
SELECT * FROM Member WHERE FirstName = 'Sam' ORDER BY Surname
An example of the query process in action:
:::php
// The SQL query isn't executed here...
$members = Member::get();
// ...or here
$members = $members->filter(array('FirstName' => 'Sam'));
// ...or even here
$members = $members->sort('Surname');
// *This* is where the query is executed
foreach($members as $member) {
echo "<p>$member->FirstName $member->Surname</p>";
}
This also means that getting the count of a list of objects will be done with a single, efficient query.
:::php
$members = Member::get()->filter(array(
'FirstName' => 'Sam'
))->sort('Surname');
// This will create an single SELECT COUNT query similar to -
// SELECT COUNT(*) FROM Members WHERE FirstName = 'Sam'
echo $members->Count();
Returning a single DataObject
There are a couple of ways of getting a single DataObject from the ORM. If you
know the ID number of the object, you can use byID($id):
:::php
$member = Member::get()->byID(5);
If you have constructed a query that you know should return a single record, you
can call First():
:::php
$member = Member::get()->filter(array(
'FirstName' => 'Sam', 'Surname' => 'Minnee'
))->First();
Sort
Quite often you would like to sort a list. Doing this on a list could be done in a few ways.
If would like to sort the list by FirstName in a ascending way (from A to Z).
:::php
$members = Member::get()->sort('FirstName', 'ASC'); // ASC or DESC
$members = Member::get()->sort('FirstName'); // Ascending is implied
To reverse the sort
:::php
$members = Member::get()->sort('FirstName', 'DESC');
// or..
$members = Member::get()->sort('FirstName', 'ASC')->reverse();
However you might have several entries with the same FirstName and would like
to sort them by FirstName and LastName
:::php
$member = Member::get()->sort(array(
'FirstName' => 'ASC',
'LastName'=>'ASC'
));
You can also sort randomly
:::php
$member = Member::get()->sort('RAND()')
Filter
As you might expect, the filter() method filters the list of objects that gets
returned. The previous example included this filter, which returns all Members
with a first name of "Sam".
:::php
$members = Member::get()->filter(array('FirstName' => 'Sam'));
In SilverStripe 2, we would have passed "\"FirstName\" = 'Sam' to make this
query. Now, we pass an array, array('FirstName' => 'Sam'), to minimize the
risk of SQL injection bugs. The format of this array follows a few rules:
- Each element of the array specifies a filter. You can specify as many filters as you like, and they all must be true.
- The key in the filter corresponds to the field that you want to filter by.
- The value in the filter corresponds to the value that you want to filter to.
So, this would return only those members called "Sam Minnée".
:::php
$members = Member::get()->filter(array(
'FirstName' => 'Sam',
'Surname' => 'Minnée',
));
There is also a short hand way of getting Members with the FirstName of Sam.
:::php
$members = Member::get()->filter('FirstName', 'Sam');
Or if you want to find both Sam and Sig.
:::php
$members = Member::get()->filter(
'FirstName', array('Sam', 'Sig')
);
Then there is the most complex task when you want to find Sam and Sig that has either Age 17 or 74.
:::php
$members = Member::get()->filter(array(
'FirstName' => array('Sam', 'Sig'),
'Age' => array(17, 74)
));
// SQL: WHERE ("FirstName" IN ('Sam', 'Sig) AND "Age" IN ('17', '74))
In case you want to match multiple criteria non-exclusively (with an "OR"
disjunctive),use the filterAny() method instead:
:::php
$members = Member::get()->filterAny(array(
'FirstName' => 'Sam',
'Age' => 17,
));
// SQL: WHERE ("FirstName" = 'Sam' OR "Age" = '17')
You can also combine both conjunctive ("AND") and disjunctive ("OR") statements.
:::php
$members = Member::get()
->filter(array(
'LastName' => 'Minnée'
))
->filterAny(array(
'FirstName' => 'Sam',
'Age' => 17,
));
// WHERE ("LastName" = 'Minnée' AND ("FirstName" = 'Sam' OR "Age" = '17'))
Exclude
The exclude() method is the opposite to the filter in that it removes entries
from a list.
If we would like to remove all members from the list with the FirstName of Sam.
:::php
$members = Member::get()->exclude('FirstName', 'Sam');
Remove both Sam and Sig is as easy as.
:::php
$members = Member::get()->exclude('FirstName', array('Sam','Sig'));
As you can see it follows the same pattern as filter, so for removing only Sam Minnée from the list:
:::php
$members = Member::get()->exclude(array(
'FirstName' => 'Sam',
'Surname' => 'Minnée',
));
And removing Sig and Sam with that are either age 17 or 74.
:::php
$members = Member::get()->exclude(array(
'FirstName' => array('Sam', 'Sig'),
'Age' => array(17, 43)
));
This would be equivalent to a SQL query of
:::
... WHERE ("FirstName" NOT IN ('Sam','Sig) OR "Age" NOT IN ('17', '74));
Search Filter Modifiers
The where clauses showcased in the previous two sections (filter and exclude)
specify exact matches by default. However, there are a number of suffixes that
you can put on field names to change this behavior such as ":StartsWith",
":EndsWith", ":PartialMatch", ":GreaterThan", ":LessThan",
":Negation".
Each of these suffixes is represented in the ORM as a subclass of
[api:SearchFilter]. Developers can define their own SearchFilters if needing
to extend the ORM filter and exclude behaviors.
These suffixes can also take modifiers themselves. The modifiers currently
supported are ":not", ":nocase" and ":case". These negate the filter,
make it case-insensitive and make it case-sensitive respectively. The default
comparison uses the database's default. For MySQL and MSSQL, this is
case-insensitive. For PostgreSQL, this is case-sensitive.
The following is a query which will return everyone whose first name doesn't start with S, who has logged in since 1/1/2011.
:::php
$members = Member::get()->filter(array(
'FirstName:StartsWith:Not' => 'S'
'Birthday:GreaterThan' => '2011-01-01'
));
Subtract
You can subtract entries from a DataList by passing in another DataList to
subtract()
:::php
$allSams = Member::get()->filter('FirstName', 'Sam');
$allMembers = Member::get();
$noSams = $allMembers->subtract($allSams);
Though for the above example it would probably be easier to use filter() and
exclude(). A better use case could be when you want to find all the members
that does not exist in a Group.
:::php
// ... Finding all members that does not belong to $group.
$otherMembers = Member::get()->subtract($group->Members());
Limit
You can limit the amount of records returned in a DataList by using the
limit() method.
:::php
// Returning the first 5 members, sorted alphabetically by Surname
$members = Member::get()->sort('Surname')->limit(5);
limit() accepts two arguments, the first being the amount of results you want
returned, with an optional second parameter to specify the offset, which allows
you to tell the system where to start getting the results from. The offset, if
not provided as an argument, will default to 0.
:::php
// Return 10 members with an offset of 4 (starting from the 5th result).
// Note that the argument order is different from a MySQL LIMIT clause
$members = Member::get()->sort('Surname')->limit(10, 4);
Raw SQL options for advanced users
Occasionally, the system described above won't let you do exactly what you need to do. In these situations, we have methods that manipulate the SQL query at a lower level. When using these, please ensure that all table & field names are escaped with double quotes, otherwise some DB back-ends (e.g. PostgreSQL) won't work.
Under the hood, query generation is handled by the [api:DataQuery] class. This
class does provide more direct access to certain SQL features that DataList
abstracts away from you.
In general, we advise against using these methods unless it's absolutely necessary. If the ORM doesn't do quite what you need it to, you may also consider extending the ORM with new data types or filter modifiers (that documentation still needs to be written)
Where clauses
You can specify a WHERE clause fragment (that will be combined with other
filters using AND) with the where() method:
:::php
$members = Member::get()->where("\"FirstName\" = 'Sam'")
Joining
You can specify a join with the innerJoin and leftJoin methods. Both of these methods have the same arguments:
- The name of the table to join to
- The filter clause for the join
- An optional alias
For example:
:::php
// Without an alias
$members = Member::get()
->leftJoin("Group_Members", "\"Group_Members\".\"MemberID\" = \"Member\".\"ID\"");
$members = Member::get()
->innerJoin("Group_Members", "\"Rel\".\"MemberID\" = \"Member\".\"ID\"", "Rel");
Passing a $join statement to DataObject::get will filter results further by
the JOINs performed against the foreign table. It will NOT return the
additionally joined data. The returned $records will always be a
[api:DataObject].
Properties
Definition
Data is defined in the static variable $db on each class, in the format:
<property-name> => "data-type"
:::php
class Player extends DataObject {
private static $db = array(
"FirstName" => "Varchar",
"Surname" => "Varchar",
"Description" => "Text",
"Status" => "Enum(array('Active', 'Injured', 'Retired'))",
"Birthday" => "Date"
);
}
See data-types for all available types.
Overloading
"Getters" and "Setters" are functions that help us save fields to our data
objects. By default, the methods getField() and setField() are used to set data
object fields. They save to the protected array, $obj->record. We can overload
the default behavior by making a function called "get<fieldname>" or
"set<fieldname>".
:::php
class Player extends DataObject {
private static $db = array(
"Status" => "Enum(array('Active', 'Injured', 'Retired'))"
);
// access through $myPlayer->Status
public function getStatus() {
// check if the Player is actually... born already!
return (!$this->obj("Birthday")->InPast()) ? "Unborn" : $this->Status;
}
Customizing
We can create new "virtual properties" which are not actually listed in
private static $db or stored in the database-row.
Here we combined a Player's first name and surname, accessible through $myPlayer->Title.
:::php
class Player extends DataObject {
public function getTitle() {
return "{$this->FirstName} {$this->Surname}";
}
// access through $myPlayer->Title = "John Doe";
// just saves data on the object, please use $myPlayer->write() to save
// the database-row
public function setTitle($title) {
list($firstName, $surName) = explode(' ', $title);
$this->FirstName = $firstName;
$this->Surname = $surName;
}
}
Default Values
Define the default values for all the $db fields. This example sets the "Status"-column on Player to "Active" whenever a new object is created.
:::php
class Player extends DataObject {
private static $defaults = array(
"Status" => 'Active',
);
}
Casting
Properties defined in static $db are automatically casted to their data-types when used in templates.
You can also cast the return-values of your custom functions (e.g. your "virtual properties"). Calling those functions directly will still return whatever type your PHP code generates, but using the obj()-method or accessing through a template will cast the value according to the $casting-definition.
:::php
class Player extends DataObject {
private static $casting = array(
"MembershipFee" => 'Currency',
);
// $myPlayer->MembershipFee() returns a float (e.g. 123.45)
// $myPlayer->obj('MembershipFee') returns a object of type Currency
// In a template: <% loop $MyPlayer %>MembershipFee.Nice<% end_loop %>
// returns a casted string (e.g. "$123.45")
public function getMembershipFee() {
return $this->Team()->BaseFee * $this->MembershipYears;
}
}
Relations
Relations are built through static array definitions on a class, in the format
<relationship-name> => <classname>.
has_one
A 1-to-1 relation creates a database-column called "<relationship-name>ID", in
the example below this would be "TeamID" on the "Player"-table.
:::php
// access with $myPlayer->Team()
class Player extends DataObject {
private static $has_one = array(
"Team" => "Team",
);
}
SilverStripe's [api:SiteTree] base-class for content-pages uses a 1-to-1
relationship to link to its parent element in the tree:
:::php
// access with $mySiteTree->Parent()
class SiteTree extends DataObject {
private static $has_one = array(
"Parent" => "SiteTree",
);
}
has_many
Defines 1-to-many joins. A database-column named ""<relationship-name>ID""
will to be created in the child-class.
:::php
// access with $myTeam->Players() or $player->Team()
class Team extends DataObject {
private static $has_many = array(
"Players" => "Player",
);
}
class Player extends DataObject {
private static $has_one = array(
"Team" => "Team",
);
}
To specify multiple $has_manys to the same object you can use dot notation to distinguish them like below
:::php
class Person extends DataObject {
private static $has_many = array(
"Managing" => "Company.Manager",
"Cleaning" => "Company.Cleaner",
);
}
class Company extends DataObject {
private static $has_one = array(
"Manager" => "Person",
"Cleaner" => "Person"
);
}
Multiple $has_one relationships are okay if they aren't linking to the same object type.
:::php
/**
* THIS IS BAD
*/
class Team extends DataObject {
private static $has_many = array(
"Players" => "Player",
);
}
class Player extends DataObject {
private static $has_one = array(
"Team" => "Team",
"AnotherTeam" => "Team",
);
}
belongs_to
Defines a 1-to-1 relationship with another object, which declares the other end
of the relationship with a corresponding $has_one. A single database column named
<relationship-name>ID will be created in the object with the $has_one, but
the $belongs_to by itself will not create a database field. This field will hold
the ID of the object declaring the $belongs_to.
Similarly with $has_many, dot notation can be used to explicitly specify the $has_one which refers to this relation. This is not mandatory unless the relationship would be otherwise ambiguous.
:::php
class Torso extends DataObject {
// HeadID will be generated on the Torso table
private static $has_one = array(
'Head' => 'Head'
);
}
class Head extends DataObject {
// No database field created. The '.Head' suffix could be omitted
private static $belongs_to = array(
'Torso' => 'Torso.Head'
);
}
many_many
Defines many-to-many joins. A new table, (this-class)_(relationship-name), will be created with a pair of ID fields.
:::php
// access with $myTeam->Categories() or $myCategory->Teams()
class Team extends DataObject {
private static $many_many = array(
"Categories" => "Category",
);
}
class Category extends DataObject {
private static $belongs_many_many = array(
"Teams" => "Team",
);
}
Adding relations
Adding new items to a relations works the same, regardless if you're editing a
has_many- or a many_many. They are encapsulated by [api:HasManyList] and
[api:ManyManyList], both of which provide very similar APIs, e.g. an add()
and remove() method.
:::php
class Team extends DataObject {
// see "many_many"-description for a sample definition of class "Category"
private static $many_many = array(
"Categories" => "Category",
);
public function addCategories(SS_List $cats) {
foreach($cats as $cat) $this->Categories()->add($cat);
}
}
Custom Relations
You can use the flexible datamodel to get a filtered result-list without writing any SQL. For example, this snippet gets you the "Players"-relation on a team, but only containing active players.
See [api:DataObject::$has_many] for more info on the described relations.
:::php
class Team extends DataObject {
private static $has_many = array(
"Players" => "Player"
);
// can be accessed by $myTeam->ActivePlayers()
public function ActivePlayers() {
return $this->Players()->filter('Status', 'Active');
}
}
Note: Adding new records to a filtered RelationList like in the example above
doesn't automatically set the filtered criteria on the added record.
Relations on Unsaved Objects
You can also set has_many and many_many relations before the DataObject is
saved. This behaviour uses the [api:UnsavedRelationList] and converts it into
the correct RelationList when saving the DataObject for the first time.
This unsaved lists will also recursively save any unsaved objects that they contain.
As these lists are not backed by the database, most of the filtering methods on
DataList cannot be used on a list of this type. As such, an
UnsavedRelationList should only be used for setting a relation before saving
an object, not for displaying the objects contained in the relation.
Validation and Constraints
Traditionally, validation in SilverStripe has been mostly handled on the controller through form validation.
While this is a useful approach, it can lead to data inconsistencies if the record is modified outside of the controller and form context.
Most validation constraints are actually data constraints which belong on the
model. SilverStripe provides the [api:DataObject->validate()] method for this
purpose.
By default, there is no validation - objects are always valid!
However, you can overload this method in your
DataObject sub-classes to specify custom validation,
or use the hook through [api:DataExtension].
Invalid objects won't be able to be written - a [api:ValidationException]` will be thrown and no write will occur.
It is expected that you call validate() in your own application to test that an object is valid before attempting a write, and respond appropriately if it isn't.
The return value of validate() is a [api:ValidationResult] object.
You can append your own errors in there.
Example: Validate postcodes based on the selected country
:::php
class MyObject extends DataObject {
private static $db = array(
'Country' => 'Varchar',
'Postcode' => 'Varchar'
);
public function validate() {
$result = parent::validate();
if($this->Country == 'DE' && $this->Postcode && strlen($this->Postcode) != 5) {
$result->error('Need five digits for German postcodes');
}
return $result;
}
}
Maps
A map is an array where the array indexes contain data as well as the values. You can build a map from any DataList like this:
:::php
$members = Member::get()->map('ID', 'FirstName');
This will return a map where the keys are Member IDs, and the values are the corresponding FirstName values. Like everything else in the ORM, these maps are lazy loaded, so the following code will only query a single record from the database:
:::php
$members = Member::get()->map('ID', 'FirstName');
echo $member[5];
This functionality is provided by the SS_Map class, which can be used to build
a map around any SS_List.
:::php
$members = Member::get();
$map = new SS_Map($members, 'ID', 'FirstName');
Note: You can also retrieve a single property from all contained records
through [api:SS_List->column()].
Data Handling
When saving data through the object model, you don't have to manually escape strings to create SQL-safe commands. You have to make sure though that certain properties are not overwritten, e.g. ID or ClassName.
Creation
:::php
$myPlayer = new Player();
$myPlayer->Firstname = "John"; // sets property on object
$myPlayer->write(); // writes row to database
Update
:::php
$myPlayer = Player::get()->byID(99);
if($myPlayer) {
$myPlayer->Firstname = "John"; // sets property on object
$myPlayer->write(); // writes row to database
}
Batch Update
:::php
$myPlayer->update(
ArrayLib::filter_keys(
$_REQUEST,
array('Birthday', 'Firstname')
)
);
Alternatively you can use castedUpdate() to respect the data-types. This is preferred to manually casting data before saving.
:::php
$myPlayer->castedUpdate(
ArrayLib::filter_keys(
$_REQUEST,
array('Birthday', 'Firstname')
)
);
onBeforeWrite
You can customize saving-behaviour for each DataObject, e.g. for adding workflow or data customization. The function is triggered when calling write() to save the object to the database. This includes saving a page in the CMS or altering a ModelAdmin record.
Example: Disallow creation of new players if the currently logged-in player is not a team-manager.
:::php
class Player extends DataObject {
private static $has_many = array(
"Teams"=>"Team"
);
public function onBeforeWrite() {
// check on first write action, aka "database row creation"
// (ID-property is not set)
if(!$this->ID) {
$currentPlayer = Member::currentUser();
if(!$currentPlayer->IsTeamManager()) {
user_error('Player-creation not allowed', E_USER_ERROR);
exit();
}
}
// check on every write action
if(!$this->record['TeamID']) {
user_error('Cannot save player without a valid team', E_USER_ERROR);
exit();
}
// CAUTION: You are required to call the parent-function, otherwise
// SilverStripe will not execute the request.
parent::onBeforeWrite();
}
}
onBeforeDelete
Triggered before executing delete() on an existing object.
Example: Checking for a specific permission to delete this type of object. It checks if a member is logged in who belongs to a group containing the permission "PLAYER_DELETE".
:::php
class Player extends DataObject {
private static $has_many = array(
"Teams"=>"Team"
);
public function onBeforeDelete() {
if(!Permission::check('PLAYER_DELETE')) {
Security::permissionFailure($this);
exit();
}
parent::onBeforeDelete();
}
}
Saving data with forms
See forms.
Saving data with custom SQL
See the "sql queries" topic for custom INSERT, UPDATE, DELETE queries.
Extending DataObjects
You can add properties and methods to existing [api:DataObjects]s like
[api:Member] (a core class) without hacking core code or subclassing. See
[api:DataExtension] for a general description, and [api:Hierarchy] for the
most popular examples.
FAQ
What's the difference between DataObject::get() and a relation-getter?
You can work with both in pretty much the same way, but relationship-getters return a special type of collection:
A [api:HasManyList] or a [api:ManyManyList] with relation-specific
functionality.
:::php
$myTeams = $myPlayer->Team(); // returns HasManyList
$myTeam->add($myOtherPlayer);