[Solved] Compilation error when using a flagable enumeration in a Q_PROPERTY

kylek

I want to create a Q_PROPERTY with my flaggable enumeration.
The code is the following :

class Car : public QObject
{
    Q_OBJECT
    Q_PROPERTY (CarOptions options READ options WRITE setOptions NOTIFY optionsChanged)
public:
    enum CarOptions
    {
        CO_None = 0x0,
        CO_AirBag = 0x1,
        CO_NavigationSystem = 0x10,
        CO_MusicPlayer = 0x100
    };

    Car(QObject *parent = 0);

    CarOptions options() const;
    void setOptions(CarOptions options);

Q_SIGNALS:
    void optionsChanged();

private:
    CarOptions _options;

public:
    Q_FLAG(CarOptions)
};

But when I compile I got the following error :

debug\moc_car.cpp: In static member function 'static void Car::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)':
debug\moc_car.cpp:119:66: error: conversion from 'QFlag' to 'Car::CarOptions' is ambiguous
     case 0: _t->setOptions(QFlag(*reinterpret_cast<int*>(_v))); break;
                                                              ^
debug\moc_car.cpp:119:66: note: candidates are:
In file included from C:\Qt\Qt5.5.0\5.5\mingw492_32\include/QtCore/qglobal.h:1102:0,
             from C:\Qt\Qt5.5.0\5.5\mingw492_32\include/QtCore/qnamespace.h:37,
             from C:\Qt\Qt5.5.0\5.5\mingw492_32\include/QtCore/qobjectdefs.h:41,
             from C:\Qt\Qt5.5.0\5.5\mingw492_32\include\QtCore/qobject.h:40,
             from C:\Qt\Qt5.5.0\5.5\mingw492_32\include\QtCore/QObject:1,
             from debug\../../test_flag_enum/car.h:4,
             from debug\moc_car.cpp:9:
C:\Qt\Qt5.5.0\5.5\mingw492_32\include/QtCore/qflags.h:66:29: note: QFlag::operator uint() const <near match>
 Q_DECL_CONSTEXPR inline operator uint() const Q_DECL_NOTHROW { return uint(i); }
                         ^
C:\Qt\Qt5.5.0\5.5\mingw492_32\include/QtCore/qflags.h:66:29: note:   no known conversion from 'uint {aka unsigned int}' to 'Car::CarOptions'
C:\Qt\Qt5.5.0\5.5\mingw492_32\include/QtCore/qflags.h:53:29: note: QFlag::operator int() const <near match>
 Q_DECL_CONSTEXPR inline operator int() const Q_DECL_NOTHROW { return i; }
                         ^
C:\Qt\Qt5.5.0\5.5\mingw492_32\include/QtCore/qflags.h:53:29: note:   no known conversion from 'int' to 'Car::CarOptions'
In file included from debug\moc_car.cpp:9:0:
debug\../../test_flag_enum/car.h:21:14: note: initializing argument 1 of 'void Car::setOptions(Car::CarOptions)'
     void setOptions(CarOptions options);

Am I missing something or is this a bug ?
Thanks.

jsulm

case 0: _t->setOptions(QFlag(*reinterpret_cast<int*>(_v))); break;
You should convert to CarOptions not to QFlags

kylek

Thanks for the answer,

The code you quote is auto generate by MOC (it's in the file 'moc_car.cpp'), can't do much here.

Chris Kawa

You're declaring your enum wrong. It should be CarOption (without the s) and then you should use Q_DECLARE_FLAGS to define the CarOptions type i.e.

...
public:
    enum CarOption
    {
        CO_None = 0x0,
        CO_AirBag = 0x1,
        CO_NavigationSystem = 0x10,
        CO_MusicPlayer = 0x100
    };
    Q_DECLARE_FLAGS(CarOptions, CarOption)
    Q_FLAG(CarOptions)
...

Btw. Not really an issue here, but flags usually use consecutive bits i.e. 0x01, 0x02, 0x04, 0x08, 0x10 and so on. You're wasting "enum space" ;)

kylek

@Chris-Kawa Tested it successfully, thanks for the info.
As for the enum, i don't know how I could mixed hexadecimal and binary format -_-

jsulm

You don't have to mix anything.
What you use in your enum are hexadecimal values not binary.
That means (left side hex, right side binary): 0x0 == 0, 0x1 == 1, 0x10 == 10000, 0x100 == 100000000!
I guess what you actually want is what Chris Kawa said: 0x01 == 1, 0x02 == 10, 0x04 == 100, 0x08 == 1000, 0x10 == 10000