about

C++11 tool for compile-time reflection utility through code generation.

Also includes some nice meta-programming utilities.

API Documentation

Doxygen output for the latest version is available here

Prerequisites

• apt-get install castxml python
• pip install pygccxml
• bazel or cmake

Supported Build Systems

• bazel
• cmake [in the future...]

How To

Write some code you want reflect

 {c++}
// test.hpp
 
#pragma once
 
namespace my_ns
{
 
struct Something
{
  float real_number;
};
 
struct SomethingElse
{
  Something a, b;
};
 
class MyClass
{
public:
  int a;
  float b;
  double c;
 
  SomethingElse d;
 
  void my_method(const char* my_arg);
 
private:
  const char* privates = "don't touch me";
};
 
enum class MyEnum
{
  VALUE_A,
  VALUE_B
};
 
}  // namespace my_ns

Setup the build

Bazel

load("//:bazel/about.bzl", "cc_library_with_reflection")
 
...
 
cc_library_with_reflection(
  name="test-about",
  hdrs=["test.hpp"],
  visibility=["//visibility:public"]
)

Use your code and the generated compile time reflection classes

Basic reflection:

Sample code:

 {c++}
 
// C++ Standard Library
#include <iostream>
#include <type_traits>
 
// About
#include <about/about.hpp>
 
// User Code (output by "test-about")
#include "test-about.meta.hpp"
 
using namespace about;
 
template<typename T>
static typename std::enable_if<has<T>("an_int"_var)>::type print_an_int(const T& object)
{
  std::cout << "This is the value of T.an_int : " << object.an_int << std::endl;
}
 
template<typename T>
static typename std::enable_if<!has<T>("an_int"_var)>::type print_an_int(const T& object)
{
  std::cout << "T doesn't have an_int" << std::endl;
}
 
int main(int argc, char const *argv[])
{
  my_ns::MyClass obj{};
  print_an_int(obj);
  return 0;
}

Output stream overloads using fmt

Sample code:

 {c++}
 
// C++ Standard Library
#include <iostream>
 
// About
#include <about/utility/fmt.hpp>
 
// User Code (output by "test-about")
#include "test-about.meta.hpp"
 
int main(int argc, char const *argv[])
{
  my_ns::MyClass obj{};
  std::cout << "my_class " << about::fmt<4>(obj) << std::endl;
  return 0;
}

Output:

my_class {
   "a" : 0,
   "b" : 0,
   "c" : 0,
   "d" : {
       "a" : {
           "real_number" : 0
       },
       "b" : {
           "real_number" : 0
       }
   }
}

Output stream overloads for enum

Sample code:

 {c++}
 
// C++ Standard Library
#include <iostream>
 
// User Code (output by "test-about")
#include "test-about.enum_ostream.hpp"
 
int main(int argc, char const *argv[])
{
  std::cout << my_ns::MyEnum::VALUE_A << ", " << my_ns::MyEnum::VALUE_B << std::endl;
  return 0;
}

Output:

MyEnum::VALUE_A, MyEnum::VALUE_B