C++ classes as instance variables of an Objective-C class

Question

I need to mix Objective-C and C++. I would like to hide all the C++ stuff inside one class and keep all the others plain Objective-C. The problem is that I want to have some C++

Answer 1

This sounds like a classic use for an interface/@protocol. Define an objective-c protocol for the API and then provide an implementation of that protocol using your Objective-C++ class. This way clients need only know about the protocol and not the header of the implementation. So given the original implementation

@interface Foo : NSObject
{
    id regularObjectiveCProperty;
    CPPClass cppStuff;

}

@end

I would define a protocol

//Extending the NSObject protocol gives the NSObject
// protocol methods. If not all implementations are
// descended from NSObject, skip this.
@protocol IFoo 

// Foo methods here
@end

and modify the original Foo declaration to

@interface Foo : NSObject 
{
    id regularObjectiveCProperty;
    CPPClass cppStuff;
}

@end

Client code can then work with type id and does not need to be compiled as Objective-C++. Obviously you can pass an instance of Foo to these clients.