When should I use signal/slot mechanism

[squidge]

I think of signal/slots as being able to reuse existing code more easily. It then doesn't depend on other classes (and doesn't care about them). Other classes can connect to it's signals and decide what methods they want to call as a result of those signals being raised.

If your class containing the signal already has a relationship with another class, and that class is the only one interested in that signal, then I see no reason to actually use signals/slots in that case. Call the method directly. It'll be faster too.