title: How to handle objective-c delegation from C++?
body: <p>Short version: I have a Qt/C++ to which I am having to add a limited amount of Cocoa/Objective-C code. I have changed the .cpp file to a .mm file and added the objective-c code/objects to said file, and it compiles and works. I now need a delegate for one of the objects I created- a NSPopUpButton (or, rather, the menu thereof) to be exact - and I'm stuck. How can I add a delegate for this object?</p>
  
  <p>Details: 
  Files in question: </p>
  
  <p>reportwindow.h, reportwindow.cpp RENAMED TO reportwindow.mm
  -These are the files containing my original C++ implementation plus some objective-c code (open a NSSavePanel containing a NSPopUpButton). reportwindow.h is additionally included in a .cpp file, if that makes a difference.</p>
  
  <p>menuHandler.h, menuHandler.mm
  -these files contain a (currently empty) objective-c class that I was intending to use as a delegate</p>
  
  <p>My first thought was that I could simply make the C++ class the delegate, but this obviously doesn't work as straight C++ doesn't understand delegation. I then thought I'd make a separate objective-c class as a NSMenuDelegate and add an instance of it as a member object to my C++ class. As I have been able to add other objective-c objects as members, I figured this should work. However, as soon as I included the header for my new objective-c class in the C++ class header file, I got several hundred errors about "expected unqualified-id before '@' token" -from the apple header files (NSValue.h, NSObject.h, etc) So apparently that didn't work, at least not as-is. I get the same result when including ANY cocoa header in my class header file.</p>
  
  <p>I then thought I'd try a forward-declaration of the objective-c class (that is how I got the other objective-c objects working). however, this didn't work either- if I declare it as "class myClassName" I get an error about re-defining the class as a different type of symbol (presumably c++ class vs objective-c protocol). If I try to forward declare it as @protocol myClassName, I get an error about "expected unqualified-id before '@' token". So how can I make this work?</p>