QJsonValue is private? - c++

Question

I am learning C++ and trying to make something. But I ran into an error and I am not sure what's up. I am trying to create a simple thing that would accept an array, and turn it into JSON. But I'm getting an error
'QJsonValue::QJsonValue(const void*)' is private
within this context
file
#include "LoginDialog.h"
#include "ui_LoginDialog.h"
LoginDialog::LoginDialog(QWidget *parent)
: QDialog(parent)
, ui(new Ui::LoginDialog)
{
setWindowFlags(Qt::FramelessWindowHint);
ui->setupUi(this);
}
LoginDialog::~LoginDialog()
{
delete ui;
}
void LoginDialog::set_socket(Socket *socket)
{
socket = socket;
QJsonArray data;
data.prepend("Hello");
socket->sendData(data);
}
void LoginDialog::on_minimize_clicked()
{
setWindowState(Qt::WindowMinimized);
}
void LoginDialog::on_quit_clicked()
{
exit(1);
}
accepting function
void Socket::sendData(QJsonArray data)
{
qDebug() << data[1];
}

Answer 1

Your problem is here:
data.prepend("Hello");
The prepend member function takes in a QJsonValue, which happens to have many constructors. Passing in a const char* makes it ambiguous as to which one you are referring to. C++ compilers will resolve this to a bool before they would resolve it to a QString. To combat this, the author of QJsonValue did this:
private:
// avoid implicit conversions from char* to bool
inline QJsonValue(const void*) {}
In any event, you can fix this problem by being more explicit:
data.prepend(QStringLiteral("Hello")); // Qt 5
data.prepend(QLatin1String("Hello")); // Qt 4, Latin1 string
data.prepend(QString("Hello")); // Qt 4, non-Latin1 string
Look here for more information about QStringLiteral.