Basic signal and slot

AsifBahrainwala

trying to better understand the signals and slots, got the code from here:-
http://doc.qt.io/qt-4.8/signalsandslots.html

for the life of me ..... it just wouldn't build
error: undefined reference to Counter::valueChanged(int)' error: undefined reference to vtable for Counter'
error: undefined reference to `vtable for Counter'

I am using the Dialog application project template
in pro

QMAKE_CXXFLAGS += -fpermissive
QMAKE_CXXFLAGS += -std=c++14

in Dialog.h

class Counter : public QObject
{
    Q_OBJECT

public:
    Counter() { m_value = 0; }

    int value() const { return m_value; }

public slots:
    void setValue(int value);

signals:
    void valueChanged(int newValue);

private:
    int m_value;
};

in dialog.cpp

void Counter::setValue(int value)
{
    if (value != m_value) {
        m_value = value;
        emit valueChanged(value);
    }
}

Edited: Added code tags - p3c0

AsifBahrainwala

I got it to work when I created separate header (Counter.h) /CPP (Counter.cpp) file , is there any way to configure the MOC to not do this........

mrjj

Hi

Moc is run on the headers
so class defs should be in the header.

Besides its recommended structure to use .h files for class
definitions as not to make huge mess.

However if you dream of not using .h files , it is possible
http://stackoverflow.com/questions/3001615/qt-moc-with-implementations-inside-of-header-files

For example: (file main.cpp)

struct SubObject : QObject
{
Q_OBJECT
};

//...

#include "main.moc"

--

The Q_OBJECT does all the magic and its ultra important to run qmake if adding this macro.