c ++类与objective-c的朋友 [英] c++ class with objective-c friend

问题描述

我有一个混合使用c ++和objective-c的应用程序。

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

很多c ++类只是作为门面访问底层目标对象从x ++应用程序的其余部分。

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.

我的问题是设计之一：目标c类需要通过一组方法调用回c ++类'd喜欢标记为私有 - 没有其他c ++类（甚至派生类）需要解决这些。

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.

但我不能标记他们的私人，因为似乎没有办法使一个c ++类的objective-c类方法的朋友。

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.

我考虑作弊和使用宏标记的c ++方法作为public，当定义 __ OBJC __ 时，会更改方法的修饰，并导致链接错误。

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.

任何人否则遇到这个？

// 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 OnPaint(CGContextRef cdc);
};

推荐答案

如果你必须这样做， C类在一个C ++对象是亲爱的CMyView。
你必须在两个类之间有另一个抽象层次。

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.

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