parent-child communication

[harry]

hi.
i have myScreen and myButton, both subclasses of QWidget. the button is a child of the screen. they need to exchange information. how can i get them to communicate?
i'm thinking something like this:

screen: i want you to be color number 2.
button: ok.

button: erm, what is color number 2?
screen: green.
button: ok, got it.

IOW. the button needs to be able to request info from the screen. but how the **** do i do that? every approach i tried has resulted in error messages.

[Chris Kawa]

Usually it's done along the lines of:

class IInfoProvider {
public:
   ...
   virtual QColor getColor(int idx) = 0;
}

class Button {
public:
   ...
   void setColor(int idx, IInfoProvider* ip) { setColorSomehow(ip->getColor(idx));  }
}

class Screen : public IInfoProvider {
   Button myButton;
public:
   ...
   QColor getColor(int idx) override {  return colorFromIndexSomehow(idx);   }

   void doStuff() { myButton.setColor(2, this);  }
}


Screen myScreen;
myScreen.doStuff();