class ReflectionFactory

class ReflectionFactory extends DefaultFactory {
    
    /**
     * {@inheritdoc}
     */
    public function createInstance($plugin_id, array $configuration = []) {
        $plugin_definition = $this->discovery
            ->getDefinition($plugin_id);
        $plugin_class = static::getPluginClass($plugin_id, $plugin_definition, $this->interface);
        // Lets figure out of there's a constructor for this class and pull
        // arguments from the $options array if so to populate it.
        $reflector = new \ReflectionClass($plugin_class);
        if ($reflector->hasMethod('__construct')) {
            $arguments = $this->getInstanceArguments($reflector, $plugin_id, $plugin_definition, $configuration);
            $instance = $reflector->newInstanceArgs($arguments);
        }
        else {
            $instance = new $plugin_class();
        }
        return $instance;
    }
    
    /**
     * Inspects the plugin class and build a list of arguments for the constructor.
     *
     * This is provided as a helper method so factories extending this class can
     * replace this and insert their own reflection logic.
     *
     * @param \ReflectionClass $reflector
     *   The reflector object being used to inspect the plugin class.
     * @param string $plugin_id
     *   The identifier of the plugin implementation.
     * @param mixed $plugin_definition
     *   The definition associated with the plugin_id.
     * @param array $configuration
     *   An array of configuration that may be passed to the instance.
     *
     * @return array
     *   An array of arguments to be passed to the constructor.
     */
    protected function getInstanceArguments(\ReflectionClass $reflector, $plugin_id, $plugin_definition, array $configuration) {
        $arguments = [];
        foreach ($reflector->getMethod('__construct')
            ->getParameters() as $param) {
            $param_name = $param->getName();
            if ($param_name == 'plugin_id') {
                $arguments[] = $plugin_id;
            }
            elseif ($param_name == 'plugin_definition') {
                $arguments[] = $plugin_definition;
            }
            elseif ($param_name == 'configuration') {
                $arguments[] = $configuration;
            }
            elseif (isset($configuration[$param_name]) || array_key_exists($param_name, $configuration)) {
                $arguments[] = $configuration[$param_name];
            }
            elseif ($param->isDefaultValueAvailable()) {
                $arguments[] = $param->getDefaultValue();
            }
            else {
                $arguments[] = NULL;
            }
        }
        return $arguments;
    }

}