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collection

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Library that offer multiple implementations of collection.

Installation

To install the package using [composer] (https://getcomposer.org/), you just need to add the following lines to your composer.json file.

...
"require": {
    "star/collection": "~1.2"
}
...

Supported collection

Enumeration

Wrap an immutable array of values in an object. Ensuring that any value passed to the enumeration is supported by the instance.

$enumeration = new Enumeration(array(1,2,3));
$enumeration->getSelected(); // returns null
$enumeration->select(2);
$enumeration->getSelected(); // returns 2
$enumeration->select('invalid'); // Throw Exception

Typed Collection

Wraps a collection of a specific kind of object (class or interface). If a value not supported by the collection is given, the collection throws exceptions.

Basic usage

$collection = new TypedCollection('\stdClass');
$collection->add(2); // Throw exception
$collection->add(new \stdClass()); // works

$collection = new TypedCollection('\Countable');
$collection->add(2); // Throw exception
$collection->add(new ClassThatImplementsCountable()); // works

Advanced usage

Using composition

Lets say that you want a Car collection, you could just define it using the basic usage, but it would lead to code duplication. So a good practice would be to define a new class named CarCollection, and use composition instead of inheritance, and declare it like this:

class CarCollection
{
    private $collection;

    public function __construct()
    {
        $this->collection = new TypedCollection('tests\Star\Component\Collection\Example\Car');
    }
}

Declaring your collection like this will enable you to encapsulate logic relevant to the car collection at one place, instead of risking to expose the inner implementation to the outside world. That way, you can control what methods are available and avoid duplication.

Using this example, adding a Car to the collection would be easy by implementing the addCar method.

class CarCollection
{
    ...
    public function addCar(Car $car)
    {
        $this->collection->add($car);
    }
    ...
}

And, if you want to filter all the cars based on their color, you can internally use it like this:

class CarCollection
{
    ...
    public function findAllCarWithColor(Color $color)
    {
        $closure = function(Car $car) use ($color) {
            return $car->getColor() == $color;
        };

        return $this->collection->filter($closure)->toArray();
    }
    ...
}

The same could also be done for finding cars based on their name:

class CarCollection
{
    ...
    public function findAllWithName($name)
    {
        $expression = Criteria::expr()->eq('name', $name);
        $criteria = new Criteria($expression);

        return $this->collection->matching($criteria)->toArray();
    }
    ...
}

From now on, your collection is re-usable, and testable at one place, while avoiding the pitfalls of inheritance.

Using Inheritance

class PassengerCollection extends TypedCollection
{
    ...
    public function findAllWithName($name)
    {
        $expression = Criteria::expr()->eq('name', $name);
        $criteria = new Criteria($expression);

        return $this->matching($criteria)->toArray();
    }
    ...
}

Using Doctrine

This class can be used in conjunction with doctrine/dbal as an added functionality, but you need to make sure that the following steps are respected.

• The custom collection should inherit from the TypedCollection which implement the Doctrine\Common\Collections\Collection.

• The collection attribute will be replaced by a Doctrine\ORM\PersistentCollection when hydrated, instead of the CustomCollection, event thought the collection is instanciated in the construct. To bypass this feature, any method that sould return a CustomCollection should be implemented like this:

  class Entity { // CustomCollection that can be hydrated with a PersistentCollection by Doctrine private $myElements;

  public function __construct()
  {
      $this->myElements = new CustomCollection('stdClass');
  }
  
  public function getElements()
  {
      // At this point $this->myElements could be a Persistent collection
      return new CustomCollection($this->myElements->toArray());
  }

  }