Silverstripe: A list decorator that allows a list to be grouped into sub-lists by number

SplitList.php

<?php
/**
 * A list decorator that allows a list to be grouped into sub-lists by number. Based on GroupBy functionality
 * @author Naomi Guyer
 */
class SplitList extends SS_ListDecorator {

	/**
	 * @param string $num
	 * @return array
	 */
	public function splitListByNum($num) {
		$result = array();
		$i = 1;

		foreach ($this->list as $item) {
			// if $item is an Object, $index can be a method or a value,
			// if $item is an array, $index is used as the index
			$key = (int)ceil($i / $num);

			if (array_key_exists($key, $result)) {
				$result[$key]->push($item);
			} else {
				$result[$key] = new ArrayList(array($item));
			}
			$i++;
		}

		return $result;
	}

	/**
	 * Similar to {@link splitListByNum()}, but returns
	 * the data in a format which is suitable for usage in templates.
	 * 
	 * @param  SS_List $list reference
	 * @param  int $num Number to split list by
	 * @param  string $children Name of the control under which children can be iterated on
	 * @return ArrayList
	 */
	public function SplitList($list, $num = 1, $children = 'Children') {
		$this->list = $list;
		$grouped = $this->splitListByNum($num);
		$result  = new ArrayList();

		$i = 1;
		foreach ($grouped as $indVal => $list) {
			$key = (int)ceil($i / $num);
			$list = GroupedList::create($list);
			$result->push(new ArrayData(array(
				$key    => $indVal,
				$children => $list
			)));
		}

		return $result;
	}

}

SplitListReadme.md

Using Split List

Copy 'SplitList.php' to your project directory. To use on your SS_Lists (eg ArrayList, DataList):

Php file with SS_List:

/*
* Groups SS_List relation "MyList" for templates
* @return ArrayList
*/
public function MyListToCol($num) {
	if(!$num) {
		$num = 1; //fall back if number is not defined
	}
	$splitList = SplitList::create($this->MyList());
	return $splitList->SplitList($this->MyList(),$num);
}

Template file (.ss)

<% loop $MyList($NumToSplitBy) %>
	<div class="row">
		<% loop $Children %>
			$Title
		<% end_loop %>
	</div>
<% end_loop %>

SplitListTest.php

<?php
/**
 * Tests for the {@link SplitList} list decorator.
 * @author Naomi Guyer
 */
class SplitListTest extends SapphireTest {

	public function testSplitListByNum() {
		$list = new SplitList(new ArrayList(array(
			array('Name' => 'AAA'),
			array('Name' => 'AAA'),
			array('Name' => 'BBB'),
			array('Name' => 'BBB'),
			array('Name' => 'AAA'),
			array('Name' => 'BBB'),
			array('Name' => 'CCC'),
			array('Name' => 'CCC')
		)));

		$split = $list->splitListByNum(4);

		$this->assertEquals(2, count($split));
		$this->assertEquals(4, count($split[1]));
		$this->assertEquals(4, count($split[2]));
	}

	public function testSplitList() {
		$list = SplitList::create(new ArrayList(array(
			array('Name' => 'AAA'),
			array('Name' => 'BBB'),
			array('Name' => 'CCC'),
			array('Name' => 'DDD'),
			array('Name' => 'EEE'),
			array('Name' => 'FFF'),
			array('Name' => 'GGG')
		)));

		$split = $list->SplitList($list, 2);
		$first   = $split->first();
		$last    = $split->last();

		$this->assertEquals(2, count($first->Children));
		$this->assertEquals('AAA', $first->Name);
		$this->assertEquals(1, count($last->Children));
		$this->assertEquals('GGG', $last->Name);
	}
}