Q_PROPERTY in a class failed when moc is running.

blaisesegbeaya

Hello All,

OS: Window 10
QT: 6.9.1
MSVC 2022
Build tool: qmake

==== Class ==
#include <QApplication>
#include <QObject>
#include <QString>

class MyClass : public QObject {

Q_OBJECT
Q_PROPERTY(QString myText READ getMyText WRITE setMyText NOTIFY myTextChanged)

public:
MyClass(QObject *parent = nullptr);

QString getMyText() const;
void setMyText(const QString &text);

signals:
void myTextChanged(const QString &newText);

private:
QString m_myText;
};

======== Implementation ==

#include <QApplication>
#include "myclass.h"

MyClass::MyClass(QObject *parent ) : QObject(parent)
{

}

QString MyClass::getMyText() const
{
return m_myText;
}

void MyClass::setMyText(const QString &text)
{
if (m_myText != text) {
m_myText = text;
emit myTextChanged(m_myText);
}
}

===== Main ===

#include "myclass.h"

int main() {
MyClass obj;
obj.setMyText("Hello");
qDebug() << obj.getMyText(); // Output: "Hello"

QObject::connect(&obj, &MyClass::myTextChanged,
                 [&](const QString &newText) {
                     qDebug() << "Text changed to:" << newText;
                 });

obj.setMyText("World"); // Output: "Text changed to: World"
return 0;

}
================= Moc error =======
cl -c -nologo -Zc:wchar_t -FS -Zc:rvalueCast -Zc:inline -Zc:strictStrings -Zc:throwingNew -permissive- -Zc:_cplusplus -Zc:externConstexpr -std:c++17 -O2 -MD -std:c++17 -utf-8 -W3 -w34100 -w34189 -w44456 -w44457 -w44458 -wd4577 -wd4467 -EHsc -DUNICODE -D_UNICODE -DWIN32 -D_ENABLE_EXTENDED_ALIGNED_STORAGE -DWIN64 -DC_PLUS_PLUS -DWin32 -DWIN32 -D_MYWINDOW -D_CRT_SECURE_NO_WARNINGS -DCPP -DQTV5 -DQTV5 -DQT5MACRO -DQt_5x -DQt_5X -DQT_5X -DQT_5x -DC_PLUS_PLUS -DCPLUSPLUS -D_CRT_SECURE_NO_WARNINGS -DSTATIC_LIB -DSTATIC_QT -DNDEBUG -DQT_NO_DEBUG -DQT_PRINTSUPPORT_LIB -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_NETWORK_LIB -DQT_SQL_LIB -DQT_CORE_LIB -I. -I. -IE:\DEV\msqlib\v6-22/bTableWidget -IE:\DEV\msqlib\v6-22/qlib -IE:\DEV\msqlib\v6-22/include -IE:\DEV\msqlib\v6-22 -I....\Qt\v6\6.9.1\msvc2022_64\include -I....\Qt\v6\6.9.1\msvc2022_64\include\QtPrintSupport -I....\Qt\v6\6.9.1\msvc2022_64\include\QtWidgets -I....\Qt\v6\6.9.1\msvc2022_64\include\QtGui -I....\Qt\v6\6.9.1\msvc2022_64\include\QtNetwork -I....\Qt\v6\6.9.1\msvc2022_64\include\QtSql -I....\Qt\v6\6.9.1\msvc2022_64\include\QtCore -IMOC -I/include -I....\Qt\v6\6.9.1\msvc2022_64\mkspecs\win32-msvc -FoOBJ\moc_myclass.obj MOC\moc_myclass.cpp
moc_myclass.cpp
....\Qt\v6\6.9.1\msvc2022_64\include\QtCore/qtmochelpers.h(262): error C2065: 'result': undeclared identifier
....\Qt\v6\6.9.1\msvc2022_64\include\QtCore/qtmochelpers.h(200): note: see reference to function template instantiation 'auto QtMocHelpers::UintData<QtMocHelpers::PropertyData<QString>>::copyTo::<lambda_930f3e387543f60f462d274f690f2e0a>::operator ()<T>(const T &) const' being compiled
with
[
T=QtMocHelpers::PropertyData<QString>
]
....\Qt\v6\6.9.1\msvc2022_64\include\QtCore/qtmochelpers.h(200): note: see reference to function template instantiation 'auto QtMocHelpers::detail::UintDataStorage<std::integer_sequence<int,0>,QtMocHelpers::PropertyData<QString>>::forEach::<lambda_f952f8e5d1a1fa6d836f8a8f79762b0c>::operator ()<QtMocHelpers::detail::UintDataEntry<0,QtMocHelpers::PropertyData<QString>>>(const QtMocHelpers::detail::UintDataEntry<0,QtMocHelpers::PropertyData<QString>> &) const' being compiled
....\Qt\v6\6.9.1\msvc2022_64\include\QtCore/qtmochelpers.h(252): note: see reference to function template instantiation 'void QtMocHelpers::detail::UintDataStorage<std::integer_sequence<int,0>,QtMocHelpers::PropertyData<QString>>::forEach<QtMocHelpers::UintData<QtMocHelpers::PropertyData<QString>>::copyTo::<lambda_930f3e387543f60f462d274f690f2e0a>>(F &&) const' being compiled
with
[
F=QtMocHelpers::UintData<QtMocHelpers::PropertyData<QString>>::copyTo::<lambda_930f3e387543f60f462d274f690f2e0a>
]
....\Qt\v6\6.9.1\msvc2022_64\include\QtCore/qtmochelpers.h(255): note: see reference to function template instantiation 'void QtMocHelpers::detail::UintDataStorage<std::integer_sequence<int,0>,QtMocHelpers::PropertyData<QString>>::forEach<QtMocHelpers::UintData<QtMocHelpers::PropertyData<QString>>::copyTo::<lambda_930f3e387543f60f462d274f690f2e0a>>(F &&) const' being compiled
with
[
F=QtMocHelpers::UintData<QtMocHelpers::PropertyData<QString>>::copyTo::<lambda_930f3e387543f60f462d274f690f2e0a>
]
....\Qt\v6\6.9.1\msvc2022_64\include\QtCore/qtmochelpers.h(550): note: see reference to function template instantiation 'void QtMocHelpers::UintData<QtMocHelpers::PropertyData<QString>>::copyTo<Unique,QtMocHelpers::MetaObjectContents<29,10,38,4>>(Result &,size_t,uint &) const' being compiled
with
[
Unique=anonymous-namespace'::qt_meta_tag_ZN7MyClassE_t, Result=QtMocHelpers::MetaObjectContents<29,10,38,4> ] ..\..\Qt\v6\6.9.1\msvc2022_64\include\QtCore/qtmochelpers.h(550): note: see reference to function template instantiation 'void QtMocHelpers::UintData<QtMocHelpers::PropertyData<QString>>::copyTo<Unique,QtMocHelpers::MetaObjectContents<29,10,38,4>>(Result &,size_t,uint &) const' being compiled with [ Unique=anonymous-namespace'::qt_meta_tag_ZN7MyClassE_t,
Result=QtMocHelpers::MetaObjectContents<29,10,38,4>
]
MOC\moc_myclass.cpp(61): note: see reference to function template instantiation 'QtMocHelpers::MetaObjectContents<29,10,38,4> QtMocHelpers::metaObjectData<MyClass,anonymous-namespace'::qt_meta_tag_ZN7MyClassE_t,QtMocHelpers::StringRefStorage<char [8],char [14],char [1],char [8],char [7]>,QtMocHelpers::UintData<QtMocHelpers::SignalData<void (const QString &)>>,QtMocHelpers::UintData<QtMocHelpers::PropertyData<QString>>,QtMocHelpers::UintData<>,QtMocHelpers::UintData<>,QtMocHelpers::detail::UintDataBlock<0,0>>(uint,const Strings &,const Methods &,const Properties &,const Enums &,const Constructors &,const ClassInfo &)' being compiled with [ Strings=QtMocHelpers::StringRefStorage<char [8],char [14],char [1],char [8],char [7]>, Methods=QtMocHelpers::UintData<QtMocHelpers::SignalData<void (const QString &)>>, Properties=QtMocHelpers::UintData<QtMocHelpers::PropertyData<QString>>, Enums=QtMocHelpers::UintData<>, Constructors=QtMocHelpers::UintData<>, ClassInfo=QtMocHelpers::detail::UintDataBlock<0,0> ] ..\..\Qt\v6\6.9.1\msvc2022_64\include\QtCore/qtmochelpers.h(550): note: while evaluating constexpr function 'QtMocHelpers::UintData<QtMocHelpers::PropertyData<QString>>::copyTo' MOC\moc_myclass.cpp(60): note: while evaluating constexpr function 'QtMocHelpers::metaObjectData' E:\DEV\temp\MOC\../myclass.h(8): note: while evaluating constexpr function 'MyClass::qt_create_metaobjectdata' E:\DEV\temp\MOC\../myclass.h(8): note: see reference to variable template 'const QtMocHelpers::MetaObjectContents<29,10,38,4> MyClass::qt_staticMetaObjectContent<anonymous namespace'::qt_meta_tag_ZN7MyClassE_t>' being compiled
MOC\moc_myclass.cpp(65): note: see reference to variable template 'const auto MyClass::qt_staticMetaObjectStaticContent<`anonymous namespace'::qt_meta_tag_ZN7MyClassE_t>' being compiled

=======
I will appreciate any help.

Axel Spoerl

Hello and welcome,
Could you please edit your post and format your code using the </> code formatting tags? It’s hard to read otherwise. Please also post the actual error. Possible that I’ve overlooked it, but I couldn’t find it.

SGaist

Hi,

One thing I could see is that setMyText is not placed under a slot directive.

blaisesegbeaya

@SGaist Thank you for your suggestion. I made the changes, and it did not change the behavior of moc.

Christian Ehrlicher

I would test it but since you did not format your code properly I won't fiddle out the mess above by myself...

blaisesegbeaya

Hello All,

It was my environment which is creating the miss behavior of moc. My building tools were pointing to the wrong version of VSVC (MSVC 2019). I corrected this, and all worked fine.

"My Culpa"

Sincerely.