Calling the method of class with unidentified type

Question

I have a class named MyClass that is subscribed by another class. When some events happen, MyClass should notify subscribers. I'm trying to use template for the subscriber's type. Because I don't want to let others(who are in charge of subscriber class) need to care about modifying MyClass for subscribing. So I've written codes below,

class MyClass {

public:

    template<typename T>
    void subscribeEvents(const T &controller)
    {
        m_subscriber = static_cast<T*>(m_subscriber);
        m_subscriber = &controller;
    }

    void notifyPositionChanged(const long &position) const {

          (m_subscriber)->onPositionChanged(position);
    }

private:

    void m_subscriber;  // will be changed to array or something else

}

Actually the controller object has a method namedonPositionChanged.

But as you know, it's not compiled for this line.

(m_subscriber)->onPositionChanged(position);

Now I understand why it's an error, but the problem is that I don't know how to modify codes or change my design. Please let me know what I'm missing and misunderstanding. Thanks in advance.

Answer 1

You dont need to use template for this. Just use a base class for your subscribers. And MyClass operate on your base class

class ISubscribe {
public:
    virtual void onPositionChanged(const long &position) = 0;
};

class MyClass {
public:

    void subscribeEvents(ISubscribe *controller)
    {
        m_subscriber = controller;
    }

    void notifyPositionChanged(const long &position) const {

      (m_subscriber)->onPositionChanged(position);
    }
private:

    ISubscribe *m_subscriber;  // will be changed to array or something else
};

class SampleSubscriber : public ISubscribe {
public :
    void onPositionChanged(const long &position) override{
              ...
    }
};

void main() {
    SampleSubscriber s;
    MyClass m;

    m.subscribeEvents(&s);
 ....
}