Creating subclass of QLabel through Qt Creator C++ Wizard?

Question

Alas, this is an embarrassingly stupid question:

Environment: Qt 5.1 Qt Creator 2.8 OSX 1.7.5;

How do I create a subclass of QLabel through the Qt Creator C++ Wizard?

Specifically, what is the base class and type information? I have tried it about three different ways and end up with various compile errors (below). Qt has been working fine so doesn't seem like an install issue so it must be a...user issue.

Answer: The base class is just QLabel and the type information is QWidget Apparently I had some other issue going on which was causing the compile errors.

---

If I set the type information to QWidget or None I get the error

symbol(s) not found for architecture x86_64

If I set the type information to QObject I get the error:

invalid conversion from 'QObject*' to 'QWidget*'

UPDATE

01:25:29: Running steps for project LabelImageTest...
01:25:29: Configuration unchanged, skipping qmake step.
01:25:29: Starting: "/usr/bin/make" 
/Applications/Xcode.app/Contents/Developer/usr/bin/g++ -c -pipe -g -gdwarf-2 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk -mmacosx-version-min=10.6 -Wall -W -fPIE -DQT_QML_DEBUG -DQT_DECLARATIVE_DEBUG -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I/Users/rise/Qt/5.1.0/clang_64/mkspecs/macx-g++ -I/Users/rise/QT_workspace/LabelImageTest -I/Users/rise/Qt/5.1.0/clang_64/include -I/Users/rise/Qt/5.1.0/clang_64/include/QtWidgets -I/Users/rise/Qt/5.1.0/clang_64/lib/QtWidgets.framework/Headers -I/Users/rise/Qt/5.1.0/clang_64/include/QtGui -I/Users/rise/Qt/5.1.0/clang_64/lib/QtGui.framework/Headers -I/Users/rise/Qt/5.1.0/clang_64/include/QtCore -I/Users/rise/Qt/5.1.0/clang_64/lib/QtCore.framework/Headers -I. -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/System/Library/Frameworks/OpenGL.framework/Versions/A/Headers -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/System/Library/Frameworks/AGL.framework/Headers -I. -I. -F/Users/rise/Qt//5.1.0/clang_64/lib -o mainwindow.o /Users/rise/QT_workspace/LabelImageTest/mainwindow.cpp
/Applications/Xcode.app/Contents/Developer/usr/bin/g++ -c -pipe -g -gdwarf-2 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk -mmacosx-version-min=10.6 -Wall -W -fPIE -DQT_QML_DEBUG -DQT_DECLARATIVE_DEBUG -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I/Users/rise/Qt/5.1.0/clang_64/mkspecs/macx-g++ -I/Users/rise/QT_workspace/LabelImageTest -I/Users/rise/Qt/5.1.0/clang_64/include -I/Users/rise/Qt/5.1.0/clang_64/include/QtWidgets -I/Users/rise/Qt/5.1.0/clang_64/lib/QtWidgets.framework/Headers -I/Users/rise/Qt/5.1.0/clang_64/include/QtGui -I/Users/rise/Qt/5.1.0/clang_64/lib/QtGui.framework/Headers -I/Users/rise/Qt/5.1.0/clang_64/include/QtCore -I/Users/rise/Qt/5.1.0/clang_64/lib/QtCore.framework/Headers -I. -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/System/Library/Frameworks/OpenGL.framework/Versions/A/Headers -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/System/Library/Frameworks/AGL.framework/Headers -I. -I. -F/Users/rise/Qt//5.1.0/clang_64/lib -o customlabel.o /Users/rise/QT_workspace/LabelImageTest/customlabel.cpp
/Users/rise/Qt/5.1.0/clang_64/bin/rcc -name images /Users/rise/QT_workspace/LabelImageTest/images.qrc -o qrc_images.cpp
/Applications/Xcode.app/Contents/Developer/usr/bin/g++ -c -pipe -g -gdwarf-2 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk -mmacosx-version-min=10.6 -Wall -W -fPIE -DQT_QML_DEBUG -DQT_DECLARATIVE_DEBUG -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I/Users/rise/Qt/5.1.0/clang_64/mkspecs/macx-g++ -I/Users/rise/QT_workspace/LabelImageTest -I/Users/rise/Qt/5.1.0/clang_64/include -I/Users/rise/Qt/5.1.0/clang_64/include/QtWidgets -I/Users/rise/Qt/5.1.0/clang_64/lib/QtWidgets.framework/Headers -I/Users/rise/Qt/5.1.0/clang_64/include/QtGui -I/Users/rise/Qt/5.1.0/clang_64/lib/QtGui.framework/Headers -I/Users/rise/Qt/5.1.0/clang_64/include/QtCore -I/Users/rise/Qt/5.1.0/clang_64/lib/QtCore.framework/Headers -I. -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/System/Library/Frameworks/OpenGL.framework/Versions/A/Headers -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/System/Library/Frameworks/AGL.framework/Headers -I. -I. -F/Users/rise/Qt//5.1.0/clang_64/lib -o qrc_images.o qrc_images.cpp
/Users/rise/Qt//5.1.0/clang_64/bin/moc -DQT_QML_DEBUG -DQT_DECLARATIVE_DEBUG -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -D__APPLE__ -D__GNUC__=4 -I/Users/rise/Qt/5.1.0/clang_64/mkspecs/macx-g++ -I/Users/rise/QT_workspace/LabelImageTest -I/Users/rise/Qt/5.1.0/clang_64/include -I/Users/rise/Qt/5.1.0/clang_64/include/QtWidgets -I/Users/rise/Qt/5.1.0/clang_64/lib/QtWidgets.framework/Headers -I/Users/rise/Qt/5.1.0/clang_64/include/QtGui -I/Users/rise/Qt/5.1.0/clang_64/lib/QtGui.framework/Headers -I/Users/rise/Qt/5.1.0/clang_64/include/QtCore -I/Users/rise/Qt/5.1.0/clang_64/lib/QtCore.framework/Headers -I. -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/System/Library/Frameworks/OpenGL.framework/Versions/A/Headers -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/System/Library/Frameworks/AGL.framework/Headers -I. -I. -F/Users/rise/Qt//5.1.0/clang_64/lib /Users/rise/QT_workspace/LabelImageTest/mainwindow.h -o moc_mainwindow.cpp
/Applications/Xcode.app/Contents/Developer/usr/bin/g++ -c -pipe -g -gdwarf-2 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk -mmacosx-version-min=10.6 -Wall -W -fPIE -DQT_QML_DEBUG -DQT_DECLARATIVE_DEBUG -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I/Users/rise/Qt/5.1.0/clang_64/mkspecs/macx-g++ -I/Users/rise/QT_workspace/LabelImageTest -I/Users/rise/Qt/5.1.0/clang_64/include -I/Users/rise/Qt/5.1.0/clang_64/include/QtWidgets -I/Users/rise/Qt/5.1.0/clang_64/lib/QtWidgets.framework/Headers -I/Users/rise/Qt/5.1.0/clang_64/include/QtGui -I/Users/rise/Qt/5.1.0/clang_64/lib/QtGui.framework/Headers -I/Users/rise/Qt/5.1.0/clang_64/include/QtCore -I/Users/rise/Qt/5.1.0/clang_64/lib/QtCore.framework/Headers -I. -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/System/Library/Frameworks/OpenGL.framework/Versions/A/Headers -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/System/Library/Frameworks/AGL.framework/Headers -I. -I. -F/Users/rise/Qt//5.1.0/clang_64/lib -o moc_mainwindow.o moc_mainwindow.cpp
/Users/rise/Qt//5.1.0/clang_64/bin/moc -DQT_QML_DEBUG -DQT_DECLARATIVE_DEBUG -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -D__APPLE__ -D__GNUC__=4 -I/Users/rise/Qt/5.1.0/clang_64/mkspecs/macx-g++ -I/Users/rise/QT_workspace/LabelImageTest -I/Users/rise/Qt/5.1.0/clang_64/include -I/Users/rise/Qt/5.1.0/clang_64/include/QtWidgets -I/Users/rise/Qt/5.1.0/clang_64/lib/QtWidgets.framework/Headers -I/Users/rise/Qt/5.1.0/clang_64/include/QtGui -I/Users/rise/Qt/5.1.0/clang_64/lib/QtGui.framework/Headers -I/Users/rise/Qt/5.1.0/clang_64/include/QtCore -I/Users/rise/Qt/5.1.0/clang_64/lib/QtCore.framework/Headers -I. -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/System/Library/Frameworks/OpenGL.framework/Versions/A/Headers -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/System/Library/Frameworks/AGL.framework/Headers -I. -I. -F/Users/rise/Qt//5.1.0/clang_64/lib /Users/rise/QT_workspace/LabelImageTest/customlabel.h -o moc_customlabel.cpp
/Applications/Xcode.app/Contents/Developer/usr/bin/g++ -c -pipe -g -gdwarf-2 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk -mmacosx-version-min=10.6 -Wall -W -fPIE -DQT_QML_DEBUG -DQT_DECLARATIVE_DEBUG -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I/Users/rise/Qt/5.1.0/clang_64/mkspecs/macx-g++ -I/Users/rise/QT_workspace/LabelImageTest -I/Users/rise/Qt/5.1.0/clang_64/include -I/Users/rise/Qt/5.1.0/clang_64/include/QtWidgets -I/Users/rise/Qt/5.1.0/clang_64/lib/QtWidgets.framework/Headers -I/Users/rise/Qt/5.1.0/clang_64/include/QtGui -I/Users/rise/Qt/5.1.0/clang_64/lib/QtGui.framework/Headers -I/Users/rise/Qt/5.1.0/clang_64/include/QtCore -I/Users/rise/Qt/5.1.0/clang_64/lib/QtCore.framework/Headers -I. -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/System/Library/Frameworks/OpenGL.framework/Versions/A/Headers -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/System/Library/Frameworks/AGL.framework/Headers -I. -I. -F/Users/rise/Qt//5.1.0/clang_64/lib -o moc_customlabel.o moc_customlabel.cpp
/Applications/Xcode.app/Contents/Developer/usr/bin/g++ -headerpad_max_install_names -Wl,-syslibroot,/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk -mmacosx-version-min=10.6 -o LabelImageTest.app/Contents/MacOS/LabelImageTest main.o mainwindow.o customlabel.o qrc_images.o moc_mainwindow.o moc_customlabel.o   -F/Users/rise/Qt//5.1.0/clang_64/lib -framework QtWidgets -F/Users/rise/Qt//5.1.0/clang_64/qtbase/lib -framework QtGui -framework QtCore -framework OpenGL -framework AGL 
ld: warning: directory not found for option '-F/Users/rise/Qt//5.1.0/clang_64/qtbase/lib'
Undefined symbols for architecture x86_64:
  "MainWindow::on_label_linkActivated(QString const&)", referenced from:
      MainWindow::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)in moc_mainwindow.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status
make: *** [LabelImageTest.app/Contents/MacOS/LabelImageTest] Error 1
01:25:34: The process "/usr/bin/make" exited with code 2.
Error while building/deploying project LabelImageTest (kit: QT 5.1)
When executing step 'Make'
01:25:34: Elapsed time: 00:05.

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Answer 1

I am not sure how you can do it from Qt Wizard,

But if you prefer code than following how it's done,

//in header file
#include <QLabel>
class MyLabel: public QLabel{
   Q_OBJECT
public:
   MyLabel( QWidget* parent=0);
   //other methods
};

//in cpp file
MyLabel::MyLabel( QWidget* parent) 
    : QLabel(parent)
{
}

You can create its instance by following code

MyLabel* label = new MyLabel();
//layout->addWidget(label);