Using Yii core collections

Yii has a set of collection classes used mainly for internal purposes which are not described in
the Definitive Guide, but are still very useful for applications:
 Lists: CList, CTypedList
Maps: CMap, CAttributeCollection
Queue: CQueue
  Stack: CStack
How to do it…
All collections implement SPL IteratorAggregate, Traversable, and Countable. Lists
and maps also implement SPL ArrayAccess. It allows using collections like a standard PHP
construct. The following is a snippet from the CList API:
ff The following is the snippet from CList API:
// append at the end
$list[]=$item;
// $index must be between 0 and $list->Count
$list[$index]=$item;
// remove the item at $index
unset($list[$index]);
// if the list has an item at $index
if(isset($list[$index]))
// traverse each item in the list
foreach($list as $index=>$item)
// returns the number of items in the list
$n=count($list);
ff CList is an integer-indexed collection. Compared to the native PHP array, it adds
stricter checks, can be used in OO fashion, and allows to make a collection read-only:
$list = new CList();
$list->add('python');
$list->add('php');
$list->add('java')
if($list->contains('php'))
$list->remove('java');
$anotherList = new CList(array('python', 'ruby'));
$list->mergeWith($anotherList);
$list->setReadOnly(true);
print_r($list->toArray());

There is another list collection named CTypedList that ensures that the list
contains only items of a certain type:
$typedList = new CTypedList('Post');
$typedList->add(new Post());
$typedList->add(new Comment());
As we are trying to add a comment to a posts list, the preceding code will give you the
following exception:
CTypedList<Post> can only hold objects of Post class.
ff CMap allows using every value, integer or not, as a key. Just like in CList, it can also
be used in the native PHP style, has almost the same set of OO-methods, and allows
making a collection read only:
$map = new CMap();
$map->add('php', array('facebook', 'wikipedia', 'wordpress',
'drupal'));
$map->add('ruby', array('basecamp', 'twitter'));
print_r($map->getKeys());
ff There is also one handy static method named CMap::mergeArray that can be used
to recursively merge two associative arrays while replacing scalar values:
$apps1 = array(
'apps' => array(
'task tracking',
'bug tracking',
),
'is_new' => false
);
$apps2 = array(
'apps' => array(
'blog',
'task tracking',
),
'todo' => array(
'buy milk',
),
'is_new' => true
);
$apps = CMap::mergeArray($apps1, $apps2);
CVarDumper::dump($apps, 10, true);
The result of the preceding code is as follows:
array
(
'apps' => array
(
'0' => 'task tracking'
'1' => 'bug tracking'
'2' => 'blog'
'3' => 'task tracking'
)
'is_new' => true
'todo' => array
(
'0' => 'buy milk'
)
)
ff CAttributeCollection includes all CMap functionality and can work with data
just like properties:
$col = new CAttributeCollection();
// $col->add('name','Alexander');
$col->name='Alexander';
// echo $col->itemAt('name');
echo $col->name;
ff CQueue and CStack implement a queue and a stack respectively. A stack works as
LIFO: last in, first out, and the queue is FIFO: first in, first out. Same as list and map
collections these can be used in native PHP style and have OO style methods:
$queue = new CQueue();
// add some tasks
$queue->enqueue(new Task('buy milk'));
$queue->enqueue(new Task('feed a cat'));
$queue->enqueue(new Task('write yii cookbook'));
// complete a task (remove from queue and return it)
echo 'Done with '.$queue->dequeue();
echo count($queue).' items left.';
// return next item without removing it
echo 'Next one is '.$queue->peek();
foreach($queue as $task)
print_r($task);
$garage = new CStack();
// getting some cars into the garage
$garage->push(new Car('Ferrari'));
$garage->push(new Car('Porsche'));
$garage->push(new Car('Kamaz'));
// Ferrari and Porsche can't get out
// since there is…
echo $garage->peek(); // Kamaz!
// we need to get Kamaz out first
$garage->pop();
$porsche = $garage->pop();
$porsche->drive();