108 lines
2.3 KiB
Markdown
108 lines
2.3 KiB
Markdown
---
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title: Managing Lists
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summary: The SS_List interface allows you to iterate through and manipulate a list of objects.
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icon: list
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---
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# Managing Lists
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Whenever using the ORM to fetch records or navigate relationships you will receive an [SS_List](api:SilverStripe\ORM\SS_List) instance commonly as
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either [DataList](api:SilverStripe\ORM\DataList) or [RelationList](api:SilverStripe\ORM\RelationList). This object gives you the ability to iterate over each of the results or
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modify.
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## Iterating over the list.
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[SS_List](api:SilverStripe\ORM\SS_List) implements `IteratorAggregate`, allowing you to loop over the instance.
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```php
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use SilverStripe\Security\Member;
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$members = Member::get();
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foreach($members as $member) {
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echo $member->Name;
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}
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```
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Or in the template engine:
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```ss
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<% loop $Members %>
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<!-- -->
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<% end_loop %>
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```
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## Finding an item by value.
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```php
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// $list->find($key, $value);
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//
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$members = Member::get();
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echo $members->find('ID', 4)->FirstName;
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// returns 'Sam'
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```
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## Maps
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A map is an array where the array indexes contain data as well as the values. You can build a map from any list
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```php
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$members = Member::get()->map('ID', 'FirstName');
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// $members = [
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// 1 => 'Sam'
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// 2 => 'Sig'
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// 3 => 'Will'
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// ];
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```
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This functionality is provided by the [Map](api:SilverStripe\ORM\Map) class, which can be used to build a map around any `SS_List`.
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```php
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$members = Member::get();
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$map = new Map($members, 'ID', 'FirstName');
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```
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## Column
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```php
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$members = Member::get();
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echo $members->column('Email');
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// returns [
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// 'sam@silverstripe.com',
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// 'sig@silverstripe.com',
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// 'will@silverstripe.com'
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// ];
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```
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## ArrayList
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[ArrayList](api:SilverStripe\ORM\ArrayList) exists to wrap a standard PHP array in the same API as a database backed list.
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```php
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$sam = Member::get()->byId(5);
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$sig = Member::get()->byId(6);
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$list = new ArrayList();
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$list->push($sam);
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$list->push($sig);
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echo $list->Count();
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// returns '2'
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```
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## Related Lessons
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* [Lists and pagination](https://www.silverstripe.org/learn/lessons/v4/lists-and-pagination-1)
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## API Documentation
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* [SS_List](api:SilverStripe\ORM\SS_List)
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* [RelationList](api:SilverStripe\ORM\RelationList)
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* [DataList](api:SilverStripe\ORM\DataList)
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* [ArrayList](api:SilverStripe\ORM\ArrayList)
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* [Map](api:SilverStripe\ORM\Map)
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