Converting c++ structure array to JSON

vsoral

I am new to this forum, so perhaps this question has been asked before.

I am using JSON (frozen) library where I need to send an array of c++ structure as a JSON string from my c++ Server to a web client application.

Are there any sample code snippets that can guide me on the usage of library to achieve this?

My c++ structure is as below:

sCPP
    {
     int l, r, s;
    }

The server application generates an array of sCPP elements, that I need to to convert to JSON string before sending to my web client.
Not very clear from the documentation.

Some example code snippets may be helpful.

thanks

mamuesp

Perhaps this part of the documentation might help. Its a good start.

nliviu

struct sCPP {
  int l, r, s;
};

static int print_sCPP(struct json_out *out, va_list *ap) {
  const struct sCPP *p = va_arg(*ap, const struct sCPP *);
  return json_printf(out, "{l: %d, r: %d, s: %d}", p->l, p->r, p->s);
}

enum mgos_app_init_result mgos_app_init(void) {
  struct sCPP data[3];
  for (size_t i = 0; i < (sizeof(data) / sizeof(data[0])); ++i) {
    data[i].l = i;
    data[i].r = i + 1;
    data[i].s = i + 2;
  }

  struct mbuf jsmb;
  struct json_out jsout = JSON_OUT_MBUF(&jsmb);
  mbuf_init(&jsmb, 0);
  json_printf(&jsout, "{data: [");
  for (size_t i = 0; i < (sizeof(data) / sizeof(data[0])); ++i) {
    json_printf(&jsout, (0==i)?"%M":", %M", print_sCPP, data+i);
  }
  json_printf(&jsout, "]}");
  LOG(LL_INFO, ("%.*s", jsmb.len, jsmb.buf));
  mbuf_free(&jsmb);
  return MGOS_APP_INIT_SUCCESS;
}

Results:

mgos_app_init        {"data": [{"l": 0, "r": 1, "s": 2}, {"l": 1, "r": 2, "s": 3}, {"l": 2, "r": 3, "s": 4}]}