silverstripe-framework/docs/en/02_Developer_Guides/00_Model/03_Lists.md

title: Managing Lists summary: The SS_List interface allows you to iterate through and manipulate a list of objects.

Managing Lists

Whenever using the ORM to fetch records or navigate relationships you will receive an [api:SS_List] instance commonly as either [api:DataList] or [api:RelationList]. This object gives you the ability to iterate over each of the results or modify.

Iterating over the list.

[api:SS_List] implements IteratorAggregate, allowing you to loop over the instance.

:::php
$members = Member::get();

foreach($members as $member) {
	echo $member->Name;
}

Or in the template engine:

:::ss
<% loop $Members %>
	<!-- -->
<% end_loop %>

Finding an item by value.

:::php
// $list->find($key, $value);

//
$members = Member::get();

echo $members->find('ID', 4)->FirstName;
// returns 'Sam'

Maps

A map is an array where the array indexes contain data as well as the values. You can build a map from any list

:::php
$members = Member::get()->map('ID', 'FirstName');

// $members = array(
//	1 => 'Sam'
//	2 => 'Sig'
//	3 => 'Will'
// );

This functionality is provided by the [api: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');

Column

:::php
$members = Member::get();

echo $members->column('Email');

// returns array(
//	'sam@silverstripe.com',
//	'sig@silverstripe.com',
//	'will@silverstripe.com'
// );

ArrayList

[api:ArrayList] exists to wrap a standard PHP array in the same API as a database backed list.

:::php
$sam = Member::get()->byId(5);
$sig = Member::get()->byId(6);

$list = new ArrayList();
$list->push($sam);
$list->push($sig);

echo $list->Count();
// returns '2'

API Documentation

• [api:SS_List]
• [api:RelationList]
• [api:DataList]
• [api:ArrayList]
• [api:SS_Map]