Question

In C++ I would like to define some strings that will be used within a class but the values will be common over all instances. In C I would have used #defines. Here is an attempt at it:

#include <string>
class AskBase {
public:
    AskBase(){}
private:
    static std::string const c_REQ_ROOT = "^Z";
    static std::string const c_REQ_PREVIOUS = "^";
    static std::string const c_REQ_VERSION = "?v";
    static std::string const c_REQ_HELP = "?";
    static std::string const c_HELP_MSG = "  ? - Help\n ?v - Version\n ^^ - Root\n  ^ - Previous\n ^Z - Exit";
};
int main(){AskBase a,b;}

If C++0x is needed that is acceptable.

Answer 1

You will have to define them separately in a single translation unit (source file), like so:

//header
class SomeClass
{
  static const std::string someString;
};

//source
const std::string SomeClass::someString = "value";

I believe the new C++1x standard will fix this, though I’m not entirely sure.