Struct with JSON in C++

Question

I’m having problems inflating a struct using a JSON file, in fact I don’t know how to do it, I’ve been researching about the Jsoncpp library, but I was not successful.

Follow a simple example of my code:

#include <iostream>

using namespace std;

struct Itens{
    int id, tipo, valor;
};

int main() {

    funcaoEncherStruct();

    return 0;
}

void funcaoEncherStruct(){
    //Segue função aqui
}

JSON file:

{
    "Itens": {
        "Produto1": {
            "id": 1,
            "tipo": 1,
            "valor": 20,
        },
        "Produto2": {
            "id": 2,
            "tipo": 3,
            "valor": 33,
        },
        "Produto3": {
            "id": 3,
            "tipo": 6,
            "valor": 60,
        }
    }
}

Answer 1

It is actually not possible to "inflate" a struct since this term defines a data structure or data type. What you’ll want to do is fill a container with objects like your struct. Another thing... it will be complicated to do what you want with this json file. The file defines an array of Items of three types, Product1, 2 and 3, I think would be simpler:

{ "Itens": 
  [
    { "id": 1, "tipo": 1, "valor": 20, }, 
    { "id": 2, "tipo": 3, "valor": 33, }, 
    { "id": 3, "tipo": 6, "valor": 60, } 
  ]
}

If you can be this json then it’s easy to popular a vector container with objects like your struct:

#include <iostream> 
#include <fstream>
#include <jsoncpp/json/json.h>

using namespace std; 

struct Item{ int id, tipo, valor; }; 

int main() { 
  vector<Item> containeritens;

  ifstream ifs("Arquivo.json");
  Json::Reader reader; 
  Json::Value obj;

  reader.parse(ifs, obj); 

  const Json::Value& itens = obj["Itens"]; 

  for (int i = 0; i < itens.size(); i++).{
    Item item;
    item.id = itens[i]["id"].asUInt();
    item.tipo = itens[i]["tipo"].asUInt();
    item.valor = itens[i]["valor"].asUInt();

    contairnerItens.pushback(item);
  }
  return 0; 
}