Quick inheritance question

Say that you have a event handler interface like

Code:

---

class KeyboardEventHandler
{
public:
  virtual bool KeyDown(const KeyboardEvent&) = 0;
  virtual bool KeyUp(const KeyboardEvent&) = 0;
};

---

and implement it something like

Code:

---

class ApplicationState
  : private KeyboardEventHandler
{
private:
  virtual bool KeyDown(const KeyboardEvent&) { return true; }
  virtual bool KeyUp(const KeyboardEvent&) { return true; }
};

---

With possible later usage looking like

Code:

---

Keyboard kb;
ApplicationState appState;

kb.RegisterEventHandler(&appState);

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Is the private inheritance kosher in this case? I want the ApplicationState to behave as-a KB event handler to recieve input, but I don't want the whole world to see the event handler functions - only the Keyboard class that will be sending the events. This compiles and runs fine with MSVC9, I just want to double check that it isn't something being enabled by an MSVC extension.

There's really not enough info here for me to answer the question.

In which function does the following take place?

Code:

---

Keyboard kb;
ApplicationState appState;

kb.RegisterEventHandler(&appState);

---

No code outside the ApplicationState class should be able to see the private base class.

I tend to use private inheritance for such event interfaces as well (influenced by a discussion here which I can't find at the moment), but with g++ I came into situation where a construct like yours led to an error message such as "the interface is not accessible". It work fine, however, if the event class registers itself.

Quote:

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Originally Posted by Richard.J

It work fine, however, if the event class registers itself.

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You know, that must've been how I did it before. I was sitting here starting to feel kinda stupid wondering why the example code didn't work after all...