Wrapping Objective C in Objective c++/c++

If you want a reusable pure C++ wrapper around an Objective C class, the Pimpl idiom works pretty well. The Pimpl idiom will make it so that there is no Objective C / Cocoa stuff visible in the header file that will be included by pure C++ code.

// FooWrapper.hpp// Absolutely no Cocoa includes or types here!class FooWrapper{public:    int bar();private:    struct Impl; // Forward declaration    Impl* impl;};// FooWrapper.mm@import "FooWraper.hpp"@import "Foundation/NSFoo.h"struct FooWrapper::Impl{    NSFoo* nsFoo;};FooWrapper::FooWrapper() : impl(new Impl){    impl->nsFoo = [[NSFoo alloc] init];}FooWrapper::~FooWrapper(){    [impl->nsFoo release];    delete impl;}int FooWrapper::bar(){    return [impl->nsFoo getInteger];}

Just mix it (but don't forget setting up the pool). It works.

 // obj-c code, in .mm file void functionContainingObjC(){        NSAutoreleasePool*pool=[[NSAutoreleasePool alloc] init];         [lots of brackets!];        [pool release]; } // c++ code, in .cc file functionContainingObjC();

objc provides c interfaces for the basic interfaces and types (#include <objc/headers_you_need.h>. therefore, you can use these interfaces in pure c/c++ TUs. then include libs like Foundation or AppKit in the mm and use objc types and messaging in the implementation.

the following is a very basic interface which is not typesafe, but i encourage you to make it typesafe for the objc type you are wrapping. this should be enough to get you started in the right direction.

// .hppnamespace MON {// could be an auto pointer or a dumb pointer; depending on your needs    class t_MONSubclassWrapper {    public:// usual stuff here...// example wrapper usage:        void release();    private:        id d_objcInstance;    };} /* << MON */// .mm...#include <Foundation/Foundation.h>MON::t_MONSubclassWrapper::t_MONSubclassWrapper() :  d_objcInstance([[MONSubclass alloc] init]) {}...void MON::t_MONSubclassWrapper::release() {    [d_objcInstance release];}