Method childOpt

tutorials/common/scenegraph/xml_parser.h:68–73

! returns child by node tag without failing */

    /*! returns child by node tag without failing */
    const Ref<XML> childOpt(const std::string& childID) const 
    {
      for (size_t i=0; i<children.size(); i++)
        if (children[i]->name == childID) return children[i];
      return null;
    }

    /*! adds a new parameter to the node */
    Ref<XML> add(const std::string& name, const std::string& val) {