将一对值与字符串进行比较

Question

config is a map within a map:

   std::map<std::string, std::map<std::string, std::string>> config;

I'm trying to parse a configuration file (.ini).

so,

config[sectionName] = map<std::string, std::string>>();
config[sectionName][optionKey] = value; //when option and value store a string.

Now,

I'm trying to implement this function. I get errors: one is that "sections == section" and " sections.second == "false" " can't be compared. The error I receive is "error: invalid operands to binary expression".

Could anyone please explain me what is wrong?

/*
 * Searches for option's value in section and converts it to a bool if possible.
 *
 * If the value isn't one of the options below or if section/option
 * don't exist the conversion fails.
 *
 * Returns a pair of <bool, bool>
 *  first is set to true if conversion succeeded, false otherwise.
 *  If the conversion succeeds, second is the converted boolean value.
 *  If the conversion fails, it doesn't matter what second is set to.
 *
 *  Converts to true: "true", "yes", "on", "1"
 *  Converts to false: "false", "no", "off", "0"
 *
 */
pair<bool, bool> ConfigParser::getBool(const string& section,
    const string& option) const
{
  for(const auto& sections : config){
    if(sections == section && sections.first != ""){

      if(sections.second == "true" || sections.second == "yes" ||
          sections.second == "on" || sections.second == "1"){

        return pair<bool, bool>(true, true);
      }
      if(sections.second == "false" || sections.second == "no" ||
          sections.second == "off" || sections.second == "0"){

        return pair<bool, bool>(true, false);
      }
    }
  }
  return pair<bool, bool>(false, false);
}

Answer 1

Consider your code fragment:

for(const auto& sections : config) {
     if(sections == section && sections.first != "") {

Here sections is a pair<string, map<string, string>> , and section is a string .

Those aren't comparable.

If you just want to look up a section section , there are much easier ways. for example:

pair<bool, bool> ConfigParser::getBool(const string& section,
                                       const string& option) const
{
    auto it = config.find(section);
    if (it == config.end()) { return {false, false}; }

    auto jt = it->second.find(option);
    if (jt == it->second->end()) { return {false, false}; }

    // parse jt->second
    return {true, /* parse result */ };
}