public function present()
    {
        $presenterClass = $this->getPresenterClass();

        if (!class_exists($presenterClass)) {
            throw new Exceptions\PresenterException('The specified presenter does not exist.');
        }

        if (!$this->presenterInstance) {
            $this->presenterInstance = new $presenterClass($this);
        }

        return $this->presenterInstance;
    }