How to change QJsonObject value in a QJson hierarchy without using copies?

Question

I am currently using Qt5.0 with the core QJson library to handle some data for the program I am developing.

To set the scene for this question I will provide you with so

Answer 1

After wasting three hours of my life I can confirm that as of today this is still impossible with Qt 5.4. You can modify JSON objects, but not nested JSON objects.

The problem is that the code such as:

json["aa"].toObject()["bb"] = 123;

essentially means the following:

QJsonObject temp = json["aa"].toObject();
temp["bb"] = 123;

and since temp is not a reference but object (and toObject() doesn't return a reference), the assignment is compiled but then discarded.

Essentially it breaks down to the fact that it is impossible to obtain the reference to an object you just created, meaning you cannot create them from left to right, i.e. aa["bb"] -> aa["bb"]["cc"] etc - you cannot obtain reference to aa["bb"], only a copy of its value.

What IS possible though is to recreate the JSON with a new value added, as described here: https://forum.qt.io/topic/25096/modify-nested-qjsonvalue/4 - note that this keeps recreating the object each time it is called, and is essentially memory usage disaster, but this is all Qt currently allows.