How to convert enum to QString? - c++

Question

I am trying to use the Qt reflection for converting enum to QString.
Here is the part of code:
class ModelApple
{
Q_GADGET
Q_ENUMS(AppleType)
public:
enum AppleType {
Big,
Small
}
}
And here is i trying to do:
convertEnumToQString(ModelApple::Big)
Return "Big"
Is this possible?
If you have any idea about convertEnumToQString, please share it

Answer 1

You need to use Q_ENUM macro, which registers an enum type with the meta-object system.
enum AppleType {
Big,
Small
};
Q_ENUM(AppleType)
And now you can use the QMetaEnum class to access meta-data about an enumerator.
QMetaEnum metaEnum = QMetaEnum::fromType<ModelApple::AppleType>();
qDebug() << metaEnum.valueToKey(ModelApple::Big);
Here is a generic template for such utility:
template<typename QEnum>
std::string QtEnumToString (const QEnum value)
{
return std::string(QMetaEnum::fromType<QEnum>().valueToKey(value));
}

Answer 2

Much more elegant way found (Qt 5.9), just one single line, with the help of mighty QVariant.
turns enum into string:
QString theBig = QVariant::fromValue(ModelApple::Big).toString();
Perhaps you don't need QMetaEnum anymore.
Sample code here:
ModelApple (no need to claim Q_DECLARE_METATYE)
class ModelApple : public QObject
{
Q_OBJECT
public:
enum AppleType {
Big,
Small
};
Q_ENUM(AppleType)
explicit ModelApple(QObject *parent = nullptr);
};
And I create a widget application, calling QVaraint function there :
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <modelapple.h>
#include <QDebug>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
QString s = QVariant::fromValue(ModelApple::Big).toString();
qDebug() << s;
}
MainWindow::~MainWindow()
{
delete ui;
}
You can see that i try to output the string on console , which really did:
And sorry for reverse casting , i tried successfully in some project , but some how this time i met compiling error. So i decide to remove it from my answer.

Answer 3

The following should get you going:
QString convertEnumToQString(ModelApple::AppleType type) {
const QMetaObject metaObject = ModelApple::staticMetaObject;
int enumIndex = metaObject.indexOfEnumerator("AppleType");
if(enumIndex == -1) {
/* The enum does not contain the specified enum */
return "";
}
QMetaEnum en = metaObject.enumerator(enumIndex);
return QString(en.valueToKey(type));
}

Answer 4

For the global Enum declaring use this in any header file:
namespace YourNamespace {
Q_NAMESPACE
enum YourEnum: int {
EnumValue1,
EnumValue2
};
Q_ENUM_NS(YourEnum)
}
and this where you want to get Enum description:
QMetaEnum metaEnum = QMetaEnum::fromType<YourEnum>();
qDebug() << "Enum description: " << metaEnum.name() << "::" << metaEnum.valueToKey(YourEnum::EnumValue2);

Answer 5

How about:
QString convertEnumToQString(ModelApple::AppleType type)
{
const QMetaObject &mo = ModelApple::staticMetaObject;
int index = mo.indexOfEnumerator("AppleType");
QMetaEnum metaEnum = mo.enumerator(index);
return metaEnum.valueToKey(type);
}
UPDATED: For Qt 5.5, see this answer

Answer 6

I faced the same problem and this is how i solved it. This is especially for Qt 4.8
QString string = enumToString(ModelApple::Big);
QString ModelApple::enumToString(AppleType apple)
{
int index = metaObject()->indexOfEnumerator("AppleType");
QMetaEnum metaEnum = metaObject()->enumerator(index);
return metaEnum.valueToKey(apple);
}