public function addChild(NodeInterface $node)
{
$name = $node->getName();
if (empty($name)) {
throw new \InvalidArgumentException('Node name cannot be empty.');
}
if (isset($this->children[$name])) {
throw new \InvalidArgumentException(sprintf('The node "%s" already exists.', $name));
}
if (null !== $this->prototype) {
throw new \RuntimeException('An ARRAY node must either have a prototype, or concrete children.');
}
$this->children[$name] = $node;
}
