lithium\util\Collection

Implements ArrayAccess
Implements Iterator
Implements Countable
class

The parent class for all collection objects. Contains methods for collection iteration, conversion, and filtering. Implements ArrayAccess, Iterator, and Countable.

Collection objects can act very much like arrays. This is especially evident in creating new objects, or by converting Collection into an actual array:

$coll = new Collection();
$coll[] = 'foo';
// $coll[0] --> 'foo'

$coll = new Collection(['data' => ['foo']]);
// $coll[0] --> 'foo'

$array = $coll->to('array');

Apart from array-like data access, Collections allow for filtering and iteration methods:

$coll = new Collection(['data' => [0, 1, 2, 3, 4]]);

$coll->first();   // 0
$coll->current(); // 0
$coll->next();    // 1
$coll->next();    // 2
$coll->next();    // 3
$coll->prev();    // 2
$coll->rewind();  // 0

The primary purpose of the Collection class is to enable simple, efficient access to groups of similar objects, and to perform operations against these objects using anonymous functions.

The map() and each() methods allow you to perform operations against the entire set of values in a Collection, while find() and first() allow you to search through values and pick out one or more.

The Collection class also supports dispatching methods against a set of objects, if the method is supported by all objects. For example:

class Task {
	public function run($when) {
		// Do some work
	}
}

$data = [
	new Task(['task' => 'task 1']),
	new Task(['task' => 'task 2']),
	new Task(['task' => 'task 3'])
];
$tasks = new Collection(compact('data'));

// $result will contain an array, and each element will be the return
// value of a run() method call:
$result = $tasks->invoke('run', ['now']);

// Alternatively, the method can be called natively, with the same result:
$result = $tasks->run('now');

Subclasses

Source

class Collection extends \lithium\core\ObjectDeprecated implements \ArrayAccess, \Iterator, \Countable {

	/**
	 * A central registry of global format handlers for `Collection` objects and subclasses.
	 * Accessed via the `formats()` method.
	 *
	 * @see lithium\util\Collection::formats()
	 * @var array
	 */
	protected static $_formats = [
		'array' => 'lithium\util\Collection::toArray'
	];

	/**
	 * The items contained in the collection.
	 *
	 * @var array
	 */
	protected $_data = [];

	/**
	 * Allows a collection's items to be automatically assigned from class construction options.
	 *
	 * @var array
	 */
	protected $_autoConfig = ['data'];

	/**
	 * Accessor method for adding format handlers to instances and subclasses of `Collection`.
	 * The values assigned are used by `Collection::to()` to convert `Collection` instances into
	 * different formats, i.e. JSON.
	 *
	 * This can be accomplished in two ways. First, format handlers may be registered on a
	 * case-by-case basis, as in the following:
	 *
	 * ```
	 * Collection::formats('json', function($collection, $options) {
	 * 	return json_encode($collection->to('array'));
	 * });
	 *
	 * // You can also implement the above as a static class method, and register it as follows:
	 * Collection::formats('json', '\my\custom\Formatter::toJson');
	 * ```
	 *
	 * Alternatively, you can implement a class that can handle several formats. This class must
	 * implement two static methods:
	 *
	 * - A `formats()` method, which returns an array indicating what formats it handles.
	 *
	 * - A `to()` method, which handles the actual conversion.
	 *
	 * Once a class implements these methods, it may be registered per the following:
	 * ```
	 * Collection::formats('\lithium\net\http\Media');
	 * ```
	 *
	 * For reference on how to implement these methods, see the `Media` class.
	 *
	 * Once a handler is registered, any instance of `Collection` or a subclass can be converted to
	 * the format(s) supported by the class or handler, using the `to()` method.
	 *
	 * @see lithium\net\http\Media::to()
	 * @see lithium\net\http\Media::formats()
	 * @see lithium\util\Collection::to()
	 * @param string $format A string representing the name of the format that a `Collection` can
	 *        be converted to. This corresponds to the `$format` parameter in the `to()` method.
	 *        Alternatively, the fully-namespaced class name of a format-handler class.
	 * @param mixed $handler If `$format` is the name of a format string, `$handler` should be the
	 *        function that handles the conversion, either an anonymous function, or a
	 *        reference to a method name in `"Class::method"` form. If `$format` is a class
	 *        name, can be `null`.
	 * @return mixed Returns the value of the format handler assigned.
	 */
	public static function formats($format, $handler = null) {
		if ($format === false) {
			return static::$_formats = ['array' => 'lithium\util\Collection::toArray'];
		}
		if ($handler === null && class_exists($format)) {
			return static::$_formats[] = $format;
		}
		return static::$_formats[$format] = $handler;
	}

	/**
	 * Initializes the collection object by merging in collection items and removing redundant
	 * object properties.
	 *
	 * @return void
	 */
	protected function _init() {
		parent::_init();
		unset($this->_config['data']);
	}

	/**
	 * Handles dispatching of methods against all items in the collection.
	 *
	 * @param string $method The name of the method to call on each instance in the collection.
	 * @param array $params The parameters to pass on each method call.
	 * @param array $options Specifies options for how to run the given method against the object
	 *        collection. The available options are:
	 *        - `'collect'`: If `true`, the results of this method call will be returned
	 *          wrapped in a new `Collection` object or subclass.
	 *        - `'merge'`: Used primarily if the method being invoked returns an array.  If
	 *          set to `true`, merges all results arrays into one.
	 * @todo Implement filtering.
	 * @return mixed Returns either an array of the return values of the methods, or the return
	 *         values wrapped in a `Collection` instance.
	 */
	public function invoke($method, array $params = [], array $options = []) {
		$class = get_class($this);
		$defaults = ['merge' => false, 'collect' => false];
		$options += $defaults;
		$data = [];

		foreach ($this as $object) {
			$value = call_user_func_array([&$object, $method], $params);
			($options['merge']) ? $data = array_merge($data, $value) : $data[$this->key()] = $value;
		}
		return ($options['collect']) ? new $class(compact('data')) : $data;
	}

	/**
	 * Hook to handle dispatching of methods against all items in the collection.
	 *
	 * @param string $method
	 * @param array $parameters
	 * @return mixed
	 */
	public function __call($method, $parameters = []) {
		return $this->invoke($method, $parameters);
	}

	/**
	 * Determines if a given method can be called.
	 *
	 * @deprecated
	 * @param string $method Name of the method.
	 * @param boolean $internal Provide `true` to perform check from inside the
	 *                class/object. When `false` checks also for public visibility;
	 *                defaults to `false`.
	 * @return boolean Returns `true` if the method can be called, `false` otherwise.
	 */
	public function respondsTo($method, $internal = false) {
		$message  = '`' . __METHOD__ . '()` has been deprecated. ';
		$message .= "Use `is_callable([Collection::first(), '<method>'])` instead.";
		trigger_error($message, E_USER_DEPRECATED);

		$magicMethod = count($this->_data) > 0 && $this->_data[0]->respondsTo($method, $internal);
		return $magicMethod || parent::respondsTo($method, $internal);
	}

	/**
	 * Converts a `Collection` object to another type of object, or a simple type such as an array.
	 * The supported values of `$format` depend on the format handlers registered in the static
	 * property `Collection::$_formats`. The `Collection` class comes with built-in support for
	 * array conversion, but other formats may be registered.
	 *
	 * Once the appropriate handlers are registered, a `Collection` instance can be
	 * converted into any handler-supported format, i.e.:
	 * ```
	 * $collection->to('json'); // returns a JSON string
	 * $collection->to('xml'); // returns an XML string
	 * ```
	 *
	 *  _Please note that Lithium does not ship with a default XML handler, but one can be
	 * configured easily._
	 *
	 * @see lithium\util\Collection::formats()
	 * @see lithium\util\Collection::$_formats
	 * @param string $format By default the only supported value is `'array'`. However, additional
	 *        format handlers can be registered using the `formats()` method.
	 * @param array $options Options for converting this collection:
	 *        - `'internal'` _boolean_: Indicates whether the current internal representation of the
	 *          collection should be exported. Defaults to `false`, which uses the standard iterator
	 *          interfaces. This is useful for exporting record sets, where records are lazy-loaded,
	 *          and the collection must be iterated in order to fetch all objects.
	 * @return mixed The object converted to the value specified in `$format`; usually an array or
	 *         string.
	 */
	public function to($format, array $options = []) {
		$defaults = ['internal' => false];
		$options += $defaults;
		$data = $options['internal'] ? $this->_data : $this;
		return $this->_to($format, $data, $options);
	}

	protected function _to($format, &$data, &$options) {
		if (is_object($format) && is_callable($format)) {
			return $format($data, $options);
		}

		if (isset(static::$_formats[$format]) && is_callable(static::$_formats[$format])) {
			$handler = static::$_formats[$format];
			$handler = is_string($handler) ? explode('::', $handler, 2) : $handler;

			if (is_array($handler)) {
				list($class, $method) = $handler;
				return $class::$method($data, $options);
			}
			return $handler($data, $options);
		}

		foreach (static::$_formats as $key => $handler) {
			if (!is_int($key)) {
				continue;
			}
			if (in_array($format, $handler::formats($format, $data, $options))) {
				return $handler::to($format, $data, $options);
			}
		}
	}

	/**
	 * Filters a copy of the items in the collection.
	 *
	 * @param callback $filter Callback to use for filtering.
	 * @param array $options The available options are:
	 *        - `'collect'`: If `true`, the results will be returned wrapped in a new
	 *          `Collection` object or subclass. Defaults to `true`.
	 * @return mixed The filtered items. Will be an array unless `'collect'` is defined in the
	 *         `$options` argument, then an instance of this class will be returned.
	 */
	public function find($filter, array $options = []) {
		$defaults = ['collect' => true];
		$options += $defaults;
		$data = array_filter($this->_data, $filter);

		if ($options['collect']) {
			$class = get_class($this);
			$data = new $class(compact('data'));
		}
		return $data;
	}

	/**
	 * Rewinds the collection and returns the first item or when a filter is used,
	 * returns the first non-empty item after the filter is applied.
	 *
	 * @see lithium\util\Collection::rewind()
	 * @param callable $filter An optional callable through which items  will be passed.
	 *        If the return value of this function is trueish, it will be returned as
	 *        the result of the method call. An example filter function may look like:
	 *        `function($item) { return $item->year < 2005; }`.
	 * @return mixed Returns the first item in the collection or when `$filter` is used,
	 *         the first item where `$filter` returned a trueish result.
	 */
	public function first($filter = null) {
		if (!$filter) {
			return $this->rewind();
		}
		foreach ($this as $item) {
			if ($filter($item)) {
				return $item;
			}
		}
	}

	/**
	 * Applies a callback to all items in the collection.
	 *
	 * @link http://php.net/array_map
	 * @param callback $filter The filter to apply.
	 * @return Collection This collection instance.
	 */
	public function each($filter) {
		$this->_data = array_map($filter, $this->_data);
		return $this;
	}

	/**
	 * Applies a callback to a copy of all data in the collection
	 * and returns the result.
	 *
	 * @link http://php.net/array_map
	 * @param callback $filter The filter to apply.
	 * @param array $options The available options are:
	 *        - `'collect'`: If `true`, the results will be returned wrapped
	 *        in a new `Collection` object or subclass.
	 * @return mixed The filtered items. Will be an array unless `'collect'` is defined in the
	 *         `$options` argument, then an instance of this class will be returned.
	 */
	public function map($filter, array $options = []) {
		$defaults = ['collect' => true];
		$options += $defaults;
		$data = array_map($filter, $this->_data);

		if ($options['collect']) {
			$class = get_class($this);
			return new $class(compact('data'));
		}
		return $data;
	}

	/**
	 * Reduce, or fold, a collection down to a single value
	 *
	 * @link http://php.net/array_reduce
	 * @param callback $reducer The reduce function, i.e. `function($carry, $item) { return ... }`
	 * @param mixed $initial Initial value passed to the reduce function as `$carry`,
	 *        defaults to `false`.
	 * @return mixed A single reduced value.
	 */
	public function reduce($reducer, $initial = false) {
		return array_reduce($this->_data, $reducer, $initial);
	}

	/**
	 * Sorts the objects in the collection.
	 *
	 * @link http://php.net/sort
	 * @link http://php.net/usort
	 * @link http://php.net/strcmp
	 * @param string|callable $sorter The sorter for the data. Either a callable to use
	 *        as the sort function or a string with the name of a well-known sort function like
	 *        `'natsort'` or a compare function like `'strcmp'`. Defaults to `'sort'`.
	 * @param array $options Reserved for future use.
	 * @return Collection Returns itself.
	 */
	public function sort($sorter = 'sort', array $options = []) {
		if (is_string($sorter) && strpos($sorter, 'sort') !== false && is_callable($sorter)) {
			call_user_func_array($sorter, [&$this->_data]);
		} elseif (is_callable($sorter)) {
			usort($this->_data, $sorter);
		}
		return $this;
	}

	/**
	 * Checks whether or not an offset exists.
	 *
	 * @param string $offset An offset to check for.
	 * @return boolean `true` if offset exists, `false` otherwise.
	 */
	public function offsetExists($offset) {
		return array_key_exists($offset, $this->_data);
	}

	/**
	 * Returns the value at specified offset.
	 *
	 * @param string $offset The offset to retrieve.
	 * @return mixed Value at offset.
	 */
	public function offsetGet($offset) {
		return $this->_data[$offset];
	}

	/**
	 * Assigns a value to the specified offset.
	 *
	 * @param string $offset The offset to assign the value to.
	 * @param mixed $value The value to set.
	 * @return mixed The value which was set.
	 */
	public function offsetSet($offset, $value) {
		if ($offset === null) {
			return $this->_data[] = $value;
		}
		return $this->_data[$offset] = $value;
	}

	/**
	 * Unsets an offset.
	 *
	 * @param string $offset The offset to unset.
	 */
	public function offsetUnset($offset) {
		prev($this->_data);
		if (key($this->_data) === null) {
			$this->rewind();
		}
		unset($this->_data[$offset]);
	}

	/**
	 * Rewinds to the first item.
	 *
	 * @return mixed The current item after rewinding, or `false` if the collection is empty.
	 */
	public function rewind() {
		return reset($this->_data);
	}

	/**
	 * Moves forward to the last item.
	 *
	 * @return mixed The last item, or `false` if there is no last item or the collection is empty.
	 */
	public function end() {
		return end($this->_data);
	}

	/**
	 * Checks if current position is valid.
	 *
	 * @return boolean `true` if valid, `false` otherwise.
	 */
	public function valid() {
		return key($this->_data) !== null;
	}

	/**
	 * Returns the current item.
	 *
	 * @return mixed The current item or `false` on failure.
	 */
	public function current() {
		return current($this->_data);
	}

	/**
	 * Returns the key of the current item.
	 *
	 * @return scalar Scalar on success or `null` on failure.
	 */
	public function key() {
		return key($this->_data);
	}

	/**
	 * Moves backward to the previous item.
	 *
	 * Note: When already at the first item, moves to the last one.
	 *
	 * @return mixed The previous item or `false` if the collection is empty. Returns the
	 *         last item, when already at the first item.
	 */
	public function prev() {
		$value = prev($this->_data);
		return key($this->_data) !== null ? $value : end($this->_data);
	}

	/**
	 * Moves forward to the next item.
	 *
	 * @return mixed The next item or `false`, in case there's no next item or the collection
	 *         is empty.
	 */
	public function next() {
		$value = next($this->_data);
		return key($this->_data) !== null ? $value : false;
	}

	/**
	 * Appends an item.
	 *
	 * @param mixed $value The item to append.
	 */
	public function append($value) {
		is_object($value) ? $this->_data[] =& $value : $this->_data[] = $value;
	}

	/**
	 * Counts the items of the object.
	 *
	 * @return integer Returns the number of items in the collection.
	 */
	public function count() {
		$count = iterator_count($this);
		$this->rewind();
		return $count;
	}

	/**
	 * Returns the item keys.
	 *
	 * @return array The keys of the items.
	 */
	public function keys() {
		return array_keys($this->_data);
	}

	/**
	 * Exports a `Collection` instance to an array. Used by `Collection::to()`.
	 *
	 * @param mixed $data Either a `Collection` instance, or an array representing a `Collection`'s
	 *        internal state.
	 * @param array $options Options used when converting `$data` to an array:
	 *        - `'handlers'` _array_: An array where the keys are fully-namespaced class
	 *        names, and the values are closures that take an instance of the class as a
	 *        parameter, and return an array or scalar value that the instance represents.
	 * @return array Returns the value of `$data` as a pure PHP array, recursively converting all
	 *         sub-objects and other values to their closest array or scalar equivalents.
	 */
	public static function toArray($data, array $options = []) {
		$defaults = ['handlers' => []];
		$options += $defaults;
		$result = [];

		foreach ($data as $key => $item) {
			switch (true) {
				case is_array($item):
					$result[$key] = static::toArray($item, $options);
				break;
				case (!is_object($item)):
					$result[$key] = $item;
				break;
				case (isset($options['handlers'][$class = get_class($item)])):
					$result[$key] = $options['handlers'][$class]($item);
				break;
				case (method_exists($item, 'to')):
					$result[$key] = $item->to('array', $options);
				break;
				case ($vars = get_object_vars($item)):
					$result[$key] = static::toArray($vars, $options);
				break;
				case (method_exists($item, '__toString')):
					$result[$key] = (string) $item;
				break;
				default:
					$result[$key] = $item;
				break;
			}
		}
		return $result;
	}
}