use the string

main.cpp

#include <QDebug>
#include <QMap>
#include <QByteArray>

class Something {
      public:
	QByteArray blob1;
	int    id2 = 0;
};

class Weird1 {
      public:
	QByteArray    name;
	uint32_t  id = 0; //Only this parameter is used to define the UNIQUENESS!!!
	Something s1;
};

bool operator<(const Weird1& e1, const Weird1& e2) {
	if (!e1.name.isEmpty() && !e2.name.isEmpty()) { //if both are set
		//compare the string
		return e1.name < e2.name;
	} else {
		//if not just use the ID
		return e1.id < e2.id;
	}
}
//to print
QDebug operator<<(QDebug debug, const Weird1& c) {
	QDebugStateSaver saver(debug);
	debug.nospace() << '(' << c.id << ", " << c.name << ')';

	return debug;
}

int main() {
	QMap<Weird1, QByteArray> qtMap;
	Weird1               k1, k2;

  //string is set, so pre-empt id
	k1.id=10;
	k1.name = "k1";

	k2.id=1;
	k2.name = "k2";

	qtMap.insert(k1, "v1");
	qtMap.insert(k2, "v2");

	qDebug() << qtMap;
}