trigger-happy/meta-json

Introduction

A set of header only libraries that make it as DRY as possible to convert between JSON strings and C++ structs.

The library depends on nlohmann-json and boost-hana to do the heavy lifting.

Caveat

Compilation times will increase significantly when this library is used due to the extensive use of C++ templates and constexpr statements. If the increase in compilation times is unacceptable, then consider not using this library in your project.

Installation

You can use this library by adding it as a submodule in your own project and telling your project's CMakeLists.txt to include the library into your own project by using the add_subdirectory command.

When building your targets, make sure you add this library as as part of the target_link_libraries command.

find_package(meta_json 1.0.0 REQUIRED)

add_executable(something something.cpp)
target_link_libraries(something meta_json::meta_json)

Converting to json

You can convert a a Hana adapted class/struct to a json string by using the meta_json::to_json function.

Converting to json

#include <meta_json/to_json.h>
#include <cassert>

struct Flat {
  int a;
  bool b;
  std::string s;
  double d;
};

BOOST_HANA_ADAPT_STRUCT(Flat, a, b, s, d);

int main() {
  Flat f{32, true, "hi", 42.42};
  auto s = meta_json::to_json(f);

  std::string json = R"({"a":32,"b":true,"d":2.2,"s":"hello"})";
  assert(s == json);

  return 0;
}

Converting from json

You can convert a json string into a Hana adapted class/struct by using the meta_json::from_json function.

Converting from json

#include <meta_json/from_json.h>
#include <cassert>

struct Flat {
  int a;
  bool b;
  std::string s;
  double d;
};

BOOST_HANA_ADAPT_STRUCT(Flat, a, b, s, d);

int main() {
  std::string json = R"({"a":32,"b":true,"d":2.2,"s":"hello"})";
  auto f = meta_json::from_json<Flat>(json);

  assert(f.a == 32);
  assert(f.b == true);
  assert(f.s == "hello");
  assert(f.d == 2.2);

  return 0;
}