双向混合目标C ++和C ++

Question

Suppose I have two objective c++ objects that each wrap a native c++ object given:
A, B = objective c++ object types
Acpp, Bcpp = c++ object types

In B.mm

#import "Bcpp.h"
#import "B.h"
@interface B ()
{
    Bcpp myBcpp; // declare instance c++ variable of type Bcpp
}
@end

In A.mm

#import "Acpp.h"
#import "A.h"
@interface A ()
{
    Acpp myAcpp; // declare instance c++ variable of type Acpp
}
@end

@implementation A
// method to return an instance of B from an instance of A (self)
- (B)GetBfromA
{
    Bcpp *bfroma = myAcpp.GetBfromA(); // return c++ object
    // How do i find the objective C++ object B from its wrapped c++ instance bfroma?

}
@end

The reason for doing this is we have a mature c++ data structure and we wish to wrap it with objective c++ objects. Is the the best way? And if it is, how do we solve the reverse mapping problem?

EDIT: Thank you to the early responders but I have a more tricky situation that I implied above. Suppose the function GetBFromA() returns an instance of Bcpp that had already been declared (as an instance variable of an instance of B). So I am holding a pointer to a Bcpp object that is itself an instance variable of an objective C++ object of type B. How do I find the instance of B from the instance of Bcpp?

Answer 1

What you probably need to do is to be able to create a B from a Bcpp . So B will need to be amended to have an -initWithBcpp: method:

- (id)initWithBcpp:(Bcpp*)bcpp
{
    self = [super init];
    if (self != nil)
    {
        myBcpp = *bcpp;
    }
    return self;
}

Then, in GetBFromA , you'll need to create a B from the Bcpp* :

- (B*)GetBfromA
{
    Bcpp *bfroma = myAcpp.GetBfromA(); // return c++ object
    B* result = [[B alloc] initWithBcpp:bfroma];
    return result;
}