请考虑成员函数模板。我的问题已嵌入评论表格中。

template<typename T>
GetValueResult GetValue(
                          const std::string &key,
                          T &val,
                          std::ios_base &(*manipulator)(std::ios_base &) = std::dec
                       )
{
   // This member function template is intended to work for all built-in
   // numeric types and std::string. However, when T = std::string, I get only
   // the first word of the map element's value. How can I fix this?

   // m_configMap is map<string, string>
   ConfigMapIter iter = m_configMap.find(key);

   if (iter == m_configMap.end())
      return CONFIG_MAP_KEY_NOT_FOUND;

   std::stringstream ss;
   ss << iter->second;

   // Convert std::string to type T. T could be std::string.
   // No real converting is going on this case, but as stated above
   // I get only the first word. How can I fix this?
   if (ss >> manipulator >> val)
      return CONFIG_MAP_SUCCESS;
   else
      return CONFIG_MAP_VALUE_INVALID;
}

最佳答案

流上的<<>>运算符旨在与由空格分隔的 token 一起使用。因此,如果字符串看起来像“1 2”,那么您的stringstream将仅在第一个1上以<<读取。

如果需要多个值,建议您在流中使用循环。这样的事情可能会做...

//stringstream has a const string& constructor
std::stringstream ss(iter->second);

while (ss >> manipulator >> value) { /* do checks here /* }

这样做之后,我建议您查看Boost,尤其是lexical_cast,它可能会开箱即用。

10-08 19:19