Using Yii core collections_Yii 1.1 Application Development Cookbook-QQ阅读男生都市网

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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:

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);

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.
```
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());
```

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'
    )
)

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;

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();