从类型 'YAML::Node&' 的右值初始化 类型的非常量引用无效 'YAML::Node'

我正在编写一个函数，该函数会将值加载并保存到.yaml文件中（取决于toggle输入的内容;"S"表示保存，"L"表示加载）。由于某种原因，我在行中收到Invalid initialization of non-const reference of type 'YAML::Node&' from an rvalue of type 'YAML::Node'错误：

YAML::Node& child = parent[*currentToken];

我在网上找到的解决方案是通过添加const关键字使其恒定。但是，就像我之前说的，我也需要能够保存价值。因此，我必须能够修改节点并且不能使其恒定。我现在应该做什么有点迷茫。我的代码为.yaml文件中的第一个节点和最后一个节点接收迭代器。这是我的代码：

bool ReadParameter(YAML::Node& parent,
        boost::tokenizer< boost::char_separator< char > >::iterator& currentToken,
        const boost::tokenizer< boost::char_separator< char > >::iterator& lastToken, float& value,
        char toggle) {
    /*
     * When we reach the last token, the distance between the iterators is 1. At this point we must
     * check to see if the token node exists in the yaml file. If it does store the value associated
     * with the token key in the variable `value` to load or store the value back into the yaml file to save.
     */
    if (distance(currentToken, lastToken) == 1) {
        if (parent[*(currentToken)].IsScalar()) {
            if (toggle == 'L') { // Load
                value = parent[*(currentToken)].as< float >();
            }
            else if (toggle == 'S') { // Save
                parent[*(currentToken)] = value;
            }
            return true;
        } else {
            printf("Key %s does not give a scalar value.n", (*currentToken).c_str());
            return false;
        }
    }
    // If the node is a map, get it's child. Else, our path does not exist.
    if (parent.IsMap()) {
        YAML::Node& child = parent[*currentToken];
        // If there is no child node, return false
        if (child.IsNull()) {
            printf("There are no more child nodes.n");
            return false;
        }
        // Iterate to the next token.
        return ReadParameter(child, ++currentToken, lastToken, value, toggle);
    } else {
        printf("Too many parameters, the parameter path is incorrect.n");
        return false;
    }
}