cpp_define_mrb_class.cpp

#include <iostream>

#include "mruby.h"
#include "mruby/data.h"
#include "mruby/compile.h"
#include "mruby/string.h"
#include "mruby/class.h"

class Application {
  public:
    inline void say() {
      std::cout << "Hello World";
    };
};

static struct mrb_data_type ApplicationType = {"Application", mrb_free};
static mrb_value appInitializer(mrb_state* mrb, mrb_value self) {
  Application* application;
  application = (Application*) DATA_PTR(self);

  if(application != NULL) {
    delete application;
  }

  DATA_TYPE(self) = &ApplicationType;
  DATA_PTR(self) = NULL;

  application = (Application*) mrb_alloca(mrb, sizeof(Application));

  DATA_PTR(self) = application;

  return self;
}

static mrb_value appSay(mrb_state*, mrb_value self) {
  Application* application = (Application*) DATA_PTR(self);
  application->say();
  return self;
}

int main(int, char**) {
  mrb_state* mrb = mrb_open();

  // mruby body
  RClass* appClass = mrb_define_class(mrb, "Application", mrb->object_class);
  mrb_define_method(mrb, appClass, "initialize", appInitializer, MRB_ARGS_NONE());
  mrb_define_method(mrb, appClass, "say", appSay, MRB_ARGS_NONE());

  mrb_load_string(mrb, "app = Application.new.say");

  if(mrb->exc) {
    mrb_value exception = mrb_obj_value(mrb->exc);
    std::cout << mrb_string_value_ptr(mrb, exception);
  }

  mrb_close(mrb);
  return 0;
}