class RequirementCollection

class RequirementCollection implements Countable, IteratorAggregate {
    
    /** @var Requirement[] */
    private $requirements = [];
    public function add(Requirement $requirement) : void {
        $this->requirements[] = $requirement;
    }
    
    /**
     * @return Requirement[]
     */
    public function getRequirements() : array {
        return $this->requirements;
    }
    public function count() : int {
        return count($this->requirements);
    }
    public function getIterator() : RequirementCollectionIterator {
        return new RequirementCollectionIterator($this);
    }

}