Is it possible to override base class signals?

Question

Qt

There is a class with a signal that provides an interface

class IA
{
signal: void sigA();
}
есть класс A реализация
class A
{
emit sigA();
}

somewhere in the main program:

IA* iterface = new A();
// тут подключаем сигнал
connect (interface, SIGNAL(sigA), this, SLOT(anySlot()));

But the slot doesn't work.
What to do with the signal so that it works in the implementation of the child?

Answer 1

Everything is quite simple (you can do the same with slots):

class IFoo
{
public:
    virtual void signal1() = 0;
    virtual void signal2() = 0;
}

class Bar : public QObject, public IFoo
{
    // ...
signals:
    void signal1();
    void signal2();
}

There is no virtual inheritance for QObject in Qt. And the bodies of purely virtual methods will be generated in moc_* files.

Answer 2

emit sigA() needs to be done. Or doesn't work?

Answer 3

If I understand you correctly:
You need to create a slot that will call the signal signA();
For example:

//Где то внутри какого-то класса
bublik slots:
  void callSignA()
  { emit signA();  }
signal:
  signA();

//Где-то в каком-то файле.cpp
QObject::connect(куПушБатон, SIGNAL(clicked), this, SLOT(signA()));
QObject::connect(this, SIGNAL(signA()), someWgt, SLOT(someSlot()));

Answer 4

General remark based on experience. On the plus side, the interface in the strict sense is rarely used; an abstract class is often needed.
To use signals in Qt, there is only one way described in the doc - to inherit from QObject