CODEWITHSUNDEEP
c++c++11templatesenable-if
Christian Ivicevic
Christian Ivicevic

Reputation: 10895

Calling std::to_string or std::to_wstring based on given typedef

In a library I am internally using typedefs of the following form:

using AnsiChar = char;
using WideChar = wchar_t;

A global typedef that basically stores the platform-specific char to be used in the entire library is defined like this:

// Either
using Char = AnsiChar;
// or
using Char = WideChar;
// depending on the platform this code is being compiled on

At some point in the code I want to either call std::to_string or std::to_wstring depending on the current Char type. My attempt looks like this:

template <typename TChar = Char, typename T>
typename std::enable_if<std::is_same<TChar, AnsiChar>::value, std::string>::type
ToString(const T& Arg)
{
    return std::to_string(Arg);
}

template <typename TChar = Char, typename T>
typename std::enable_if<std::is_same<TChar, WideChar>::value, std::wstring>::type
ToString(const T& Arg)
{
    return std::to_wstring(Arg);
}

Is this the correct way to implement a conditional function or is there any other way that is recommended to accomplish this?

EDIT. As a side-note I was considering to work with function pointers using something like std::basic_string<Char> as the return type to generalize this and then somehow conditionally bind either of std::to_string or std::to_wstring to the pointer.

Upvotes: 2

Views: 1123

Answers (1)

Yakk - Adam Nevraumont
Yakk - Adam Nevraumont

Reputation: 275820

template<class Char>
struct string_traits;
template<>
struct string_traits<char>{
  using string=std::string;
  template<class T>
  static string convert_to_string(T&& t){
    using std::to_string;
    return to_string(std::forward<T>(t));
  }
};
template<>
struct string_traits<wchar_t>{
  using string=std::wstring;
  template<class T>
  static string convert_to_string(T&& t){
    using std::to_wstring;
    return to_wstring(std::forward<T>(t));
  }
};

now your code is simply

template <typename TChar = Char, typename T>
std::basic_string<TChar>
ToString(const T& Arg) {
  return string_traits<TChar>::convert_to_string(Arg);
}

Upvotes: 1

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