How to get QJsonObject values in order? - c++

Question

I want to use Json in Qt and my data inside the QJsonObject must be in some particular order since we have some confirmation method via a token and getting a hash of the Json.
Since QJsonObject sorts its key-value pairs in alphabetical order I something like this to happen:
QJsonObject object;
object.insert("B","b");
object.insert("A","a");
qDebug() << QJsonDocument(object).toJson(); // this-line
I want this-line to printout something like this:
{"B":"b","A":"a"}
but instead i get this:
{
"A":"a",
"B":"b"
}
I have written a class:
jsonobject.h
class JsonObject
{
public:
JsonObject();
void insert(QString key,QJsonValue value);
void remove(QString key);
QString toJsonString();
QString convertQJsonValue2String(QJsonValue value);
QString convertQJsonArray2String(QJsonArray array);
QString convertQJsonObject2String(QJsonObject object);
private:
void appendKey(QString key,QString * out);
QJsonObject qJsonObject;
QStringList keysInOrder;
};
jsonobject.cpp
#include "jsonobject.h"
JsonObject::JsonObject()
{
keysInOrder.clear();
}
void JsonObject::insert(QString key, QJsonValue value)
{
if(!keysInOrder.contains(key))
keysInOrder.append(key);
qJsonObject.insert(key,value);
}
void JsonObject::remove(QString key)
{
keysInOrder.removeOne(key);
qJsonObject.remove(key);
}
QString JsonObject::toJsonString()
{
QString out;
for(int i = 0 ; i < keysInOrder.size() ; i++)
{
appendKey(keysInOrder[i],&out);
out.append(convertQJsonValue2String(qJsonObject.value(keysInOrder[i])));
if(i != (keysInOrder.size() - 1))
out.append(",");
}
return out.prepend("{").append("}");
}
QString JsonObject::convertQJsonObject2String(QJsonObject object)
{
QStringList keys = object.keys();
QString out;
for(int i = 0 ; i < keys.size() ; i++)
{
appendKey(keys[i],&out);
out.append(convertQJsonValue2String(object[keys[i]]));
if(i != keys.size() - 1)
out.append(",");
}
return out.prepend("{").append("}");
}
void JsonObject::appendKey(QString key, QString *out)
{
out->append("\"");
out->append(key);
out->append("\"");
out->append(":");
}
QString JsonObject::convertQJsonValue2String(QJsonValue value)
{
switch(value.type())
{
case QJsonValue::Null:
return QString("null");
break;
case QJsonValue::Bool:
return QString("%1").arg(value.toBool());
break;
case QJsonValue::Double:
return QString("%1").arg(value.toDouble());
break;
case QJsonValue::String:
return value.toString().prepend("\"").append("\"");
break;
case QJsonValue::Object:
return convertQJsonObject2String(value.toObject());
break;
case QJsonValue::Array:
return convertQJsonArray2String(value.toArray());
break;
case QJsonValue::Undefined:
return QString();
break;
}
return QString();
}
QString JsonObject::convertQJsonArray2String(QJsonArray array)
{
QString out;
for(int i = 0 ; i < array.size() ; i++)
{
QJsonValue value = array.at(i);
out.append(convertQJsonValue2String(value));
if(i != (array.size() - 1))
out.append(",");
}
return out.prepend("[").append("]");
}
the problem here is that I have QJsonObjects inside and my converQJSonObject2String(QJsonObject object) still don't have that order.

Answer 1

To me this looks like you're trying to use json for something it is not meant to do. Json does not have a canonical representation, so even if you manage to order the keys correctly, you might still run into problems. (Keys with non-ascii characters, whitespace differences, ...)
While it is certainly possible to do what you're looking for (I suggest using another library that offers this possibility), try to take a step back and think about what you're trying to achieve.
Would it be possible to take the hash of the json you receive from the server directly?