SmartEnum.h

/* Distributed under the Apache License, Version 2.0.
   See accompanying NOTICE file for details.*/
 
#pragma once
 
#include <iostream>
#include <sstream>
#include <string>
#include <algorithm>
#include <vector>
#include <iterator>
 
// Not sure why I have such a facination with enums, but..
// This is a bit of a pet project, I have been curious to see how one can make
// and enum that both, has string mappings and is iterable
// It would really be nice to have unbound wildcard templates in C++ some how...
// I really want to be able to have a compartment manager be populated with
// a set of compartments defined in a custom enum definition
// and have the compartment manager getCompartment method take in the custom type
// And allow for support of multiple custom types.. 
// At anyrate, I am only using this in unit testing
// Found these articles that helped come up with this junk
// http://www.cprogramming.com/c++11/c++11-nullptr-strongly-typed-enum-class.html
// http://www.cprogramming.com/tutorial/template_specialization.html
// http://codereview.stackexchange.com/questions/57626/iterable-enum-class-in-c11
// http://codereview.stackexchange.com/questions/14309/conversion-between-enum-and-string-in-c-class-header?rq=1
// http://stackoverflow.com/questions/6288812/template-in-c
 
// This is the type that will hold all the strings.
// Each enumerate type will declare its own specialization.
// Any enum that does not have a specialization will generate a compiler error
// indicating that there is no definition of this variable (as there should be
// be no definition of a generic version).
template<typename T>
struct enumStrings
{
  static char const* values[];
};
 
// Here is a base class that works via an index and string
struct SmartEnum
{
  virtual int index() const = 0;
  virtual const std::string& string() const = 0;
};
 
// Here are is a macro to fill out the contents of a SmartEnum struct
// You only need to provide the struct, the enum associated (and how many)
// and the strings mapped to those enums
 
#define SMART_ENUM(Clazz, Type, Length) \
 static constexpr std::size_t _size = Length; \
\
  Clazz() : _idx(0) {} \
  Clazz(Type t) { _idx = static_cast<Type>(t); } \
  virtual ~Clazz() {} \
\
  int index() const { return _idx; } \
  Type value() const { return Type(_idx); } \
  const char* string() const { return Clazz::Value(_idx); } \
  void set(const Type& t) { _idx = static_cast<int>(t); } \
\
  Type        operator++() { if (_idx != (_size - 1)) _idx++;  return Type(_idx); } \
  Type        operator++(int) { if (_idx != (_size - 1)) _idx++;  return Type(_idx); } \
  bool        operator==(Clazz const& rhs) { return _idx == rhs._idx; } \
  bool        operator!=(Clazz const& rhs) { return _idx != rhs._idx; } \
protected: \
  int    _idx; \
public:   
 
// Here is an example (You don't need to derive from SmartEnum if you don't want to)
//struct ExampleEnum : public SmartEnum
//{
//  // NOTE, THESE ENUMS MUST BE OF THE DEFAULT INDEXING (You can't say enum Type {A=10, B=30 }
//  enum Type { A, B, C };
//  SMART_ENUM(ExampleEnum, Type, 3);
//  static char const* Value(size_t idx);
//};// Length of enum and values[] must be the same, and reflected in the input to SMART_ENUM
// Put this in your cpp file
//template<> char const* enumStrings<ExampleEnum>::values[] = { "Alpha", "Bravo", "Charlie" };
//char const* ExampleEnum::Value(size_t idx)
//{
//  return enumStrings<ExampleEnum>::values[idx];
//}
//NOTE: You can also templitize this class with the enum type if you want, but how to you set the size?
//I will figure that out when/if I need it