Serialization QList<MyObject> to JSON

Question

I've problem, I tried searched online like convert QList to JSON, and send it to URL, but first, I don't found nothing about serialise QList<Myobject> to json with Qt and C++.

My not empty QList:

QList<User> lista;

my target is lista to JSON.

How to serialize it? I've saw online that QJson exists, but is an external compenent... there is a internal component within Qt 5.9?

Answer 1

an external compenent

Qt has internal JSON support.

First you need to provide a QJsonValue representation for the object itself, and then iterate the list and convert it to e.g. an array. Use QJsonDocument to convert it to text:

// https://github.com/KubaO/stackoverflown/tree/master/questions/json-serialize-44567345
#include <QtCore>
#include <cstdio>

struct User {
   QString name;
   int age;
   QJsonObject toJson() const {
      return {{"name", name}, {"age", age}};
   }
};

QJsonArray toJson(const QList<User> & list) {
   QJsonArray array;
   for (auto & user : list)
      array.append(user.toJson());
   return array;
}

int main() {
   QList<User> users{{"John Doe", 43}, {"Mary Doe", 44}};
   auto doc = QJsonDocument(toJson(users));
   std::printf("%s", doc.toJson().constData());
}

Output:

[
    {
        "age": 43,
        "name": "John Doe"
    },
    {
        "age": 44,
        "name": "Mary Doe"
    }
]