public function addLoader($extensions, $loaderClass)
{
foreach ((array) $extensions as $extension) {
$this->extensions[] = $extension;
if (is_string($loaderClass)) {
$this->loaderClasses[$extension] = $loaderClass;
} elseif ($loaderClass instanceof LoaderInterface) {
$this->loaders[$extension] = $loaderClass;
}
}
}