How do I 'ToString()' an enum in C++? [duplicate]

Question

How do I 'ToString()' an enum in C++?

In Java and C# I would just call ToString.

enum Colours
{
    Red =0,
    Green=1,
    Blue=2
};

I need to create a string like: "Invalid colour '" + colour + "' selected."

Answer 1

While this is commonly done through switches, I prefer arrays:

#include <iostream>

namespace foo {
  enum Colors { BLUE = 0, RED, GREEN, SIZE_OF_ENUM };
  static const char* ColorNames[] = { "blue", "red", "green" };

  // statically check that the size of ColorNames fits the number of Colors
  static_assert(sizeof(foo::ColorNames)/sizeof(char*) == foo::SIZE_OF_ENUM
    , "sizes dont match");
} // foo

int main()
{
  std::cout << foo::ColorNames[foo::BLUE] << std::endl;
  return 0;
}

The explicit array size has the benefit of generating a compile time error should the size of the enum change and you forget to add the appropriate string.

Alternatively, there is Boost.Enum in the Boost vault. The library hasn't been officially released but is quite stable and provides what you want. I wouldn't recommend it to a novice though.