CODEWITHSUNDEEP
c++objective-c
Chris Becke
Chris Becke

Reputation: 36026

c++ class with objective-c friend

I have an application thats a mix of c++ and objective-c.

Quite a lot of the c++ classes exist merely as facades to access the underlying objective-c object from the rest of the x++ application.

My problem is one of design: The objective-c class needs to call back into the c++ class via a set of methods I'd prefer to mark as private - no other c++ class (not even derived classes) needs to be messing around with these.

But I can't mark them private, as there doesn't seem to be a way to make objective-c class methods 'friends' of a c++ class.

I considered cheating and using macro's to mark the c++ methods as public when __OBJC__ is defined, but that changes the method's decoration and would result in link errors.

anyone else encountered this?

// MyView.mm
@interface MyView : NSView {
@public
  CMyView* _cpp;
}

-(void)drawRect:(NSRect)dirtyRect {
  CGContextRef cgc = (CGContextRef)[[NSGraphicsContext currentContext]graphicsPort];
  _cpp->Draw(cgc);
}
...

// MyView.h
class CMyView {
  id _view; 
public:
  // this method should be private. It exists ONLY for the MyView obj-c class.
  void Draw(CGContextRef cdc);
};

Upvotes: 13

Views: 2609

Answers (1)

Joshua Weinberg
Joshua Weinberg

Reputation: 28688

If you must do that you can wrap your Obj-C class in a C++ object that is friended to CMyView. You'd need another level of abstraction between the two classes you have already.

Upvotes: 8

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