How to convert an unsigned long int to QVariant

Question

I have realized that QVariant does not offer functionality for long and unsigned long. It offers conversions to int, unsigned int, long long and unsigned long long.

We can find in current Desktop architectures that long and int are equivalent, but they are not from a theoretical point of view.

If I want to store a long in a QVariant I am obligated to convert first the value to long long. I would like to know if there is any other way to overcome this.

Secondly, I am interested to know the better/simpler way to do it. I.e. using a simpler code, and avoiding the use of unnecessary space or instructions.

Answer 1

It's very likely (according to the question title) that topic starter has received the following error message from the compiler:

    error: conversion from ‘uint64_t {aka long unsigned int}’ to ‘QVariant’ is ambiguous

None of the answers suggested provides a simple solution. So, instead of implicit conversion from a value, something like

    QVariant_value = long_unsigned_int_value;

try the following:

    QVariant_value = QVariant::fromValue(long_unsigned_int_value)

This helped me.

Answer 2

If I want to store a long in a QVariant, I am obligated to convert first the value to long long.

 QVariant store (unsigned long int input) {
    unsigned long long data = (unsigned long long) input;
    QVariant qvariant( data );
    return qvariant;
 }

 unsigned long int load (const QVariant& qvariant) {
    bool ok;
    unsigned long int data = (unsigned long) qvariant.toULongLong(&ok);
    if (ok)
       return data;
    else
       return NAN;
 }