How to define signals with macros in Qt

Question

I try to create a some standart signal definitionsfor some classes with macros like:

#define CREATE_SIGNALS signals: void error_signal(QString error);

Functions are created, but moc did not create methods for these functions. It seems that moc is running before macros processed. How can i make this work?

You probably cannot do what you want (and use `moc`). Please **edit your question** to give the actual real case and *motivate* your question. — Basile Starynkevitch, Jun 29 '16 at 18:23

score 4 · Accepted Answer · answered Jun 29 '16 at 18:32

Moc preprocesses the sources it works on, so your macro will work once you actually make the macro define some signals, and not regular methods.

The following is a complete example:

#include <QtCore>
#include <array>
#include <algorithm>

#define CREATE_SIGNALS\
   Q_SIGNAL void signal1(const QString & = QString());\
   Q_SIGNAL void signal2(int = 0);

struct Foo : QObject {
   CREATE_SIGNALS
   Q_OBJECT
};

struct Bar : QObject {
   CREATE_SIGNALS
   Q_OBJECT
};

int main()
{
   std::array<int, 4> s;
   Foo foo;
   Bar bar;
   s.fill(0);
   QObject::connect(&foo, &Foo::signal1, [&]{++s[0];});
   QObject::connect(&foo, &Foo::signal2, [&]{++s[1];});
   QObject::connect(&bar, &Bar::signal1, [&]{++s[2];});
   QObject::connect(&bar, &Bar::signal2, [&]{++s[3];});
   emit foo.signal1();
   emit foo.signal2();
   emit bar.signal1();
   emit bar.signal2();
   Q_ASSERT(std::all_of(std::begin(s), std::end(s), [](int val) { return val == 1; }));
}

#include "main.moc"

Actually, i wrote macro as #define CREATE_SIGNALS signals: void error_signal(QString error); it was not working,but after Q_SIGNAL it is working now. — fyo, Jun 29 '16 at 18:42
@fyo The Q_SIGNAL and Q_SLOT are guaranteed to work in all cases. — Kuba hasn't forgotten Monica, Jun 29 '16 at 18:53

How to define signals with macros in Qt

1 Answers1