Sending signal from static class method in Qt

Question

I am trying to code a static callback function that is called frequently from another static function within the same class. My callback function needs to emit

Answer 1

That is not going to work, because you are creating a new Foo every time you enter that static function, and you do not connect a signal to a slot.

So, the fix would be to pass the object to that function :

class Foo
{
signals:
    emitFunction(int);
private:
    static int callback(int val, Foo &foo)
    {
        /* Called multiple times (100+) */
        foo.emitFunction(val);
    }
    void run()
    {
        callback(percentdownloaded, *this);
    }
};

Another option is to use postEvent, but I wouldn't recommend it.

---

Since you can not modify callback's signature, you can do it like this :

class Foo
{
signals:
    emitFunction(int);
private:
    static int callback(int val)
    {
        /* Called multiple times (100+) */
        theFoo->emitFunction(val);
    }
    static Foo *theFoo;
    void run()
    {
        callback(percentdownloaded, *this);
    }
};

but you'll have to initialize that static variable somewhere.