Nullable values in C++

Question

I\'m creating a database access layer in native C++, and I\'m looking at ways to support NULL values. Here is what I have so far:

class CNullValue
{
public:         


        

Answer 1

There are lot of Nullable type implementation for C++ and most are incomplete. In C++ world, nullable types are called optional types. This was proposed for C++14 but got postponed. However the code to implement it compiles and works on most C++11 compilers. You can just drop in the single header file implementing optional type and start using it:

https://raw.githubusercontent.com/akrzemi1/Optional/master/optional.hpp

Sample usage:

#if (defined __cplusplus) && (__cplusplus >= 201700L)
#include 
#else
#include "optional.hpp"
#endif

#include 

#if (defined __cplusplus) && (__cplusplus >= 201700L)
using std::optional;
#else
using std::experimental::optional;
#endif

int main()
{
    optional o1,      // empty
                  o2 = 1,  // init from rvalue
                  o3 = o2; // copy-constructor

    if (!o1) {
        cout << "o1 has no value";
    } 

    std::cout << *o2 << ' ' << *o3 << ' ' << *o4 << '\n';
}

More documentation: http://en.cppreference.com/w/cpp/experimental/optional

Also see my other answer: https://stackoverflow.com/a/37624595/207661