C++ Callbacks with objective-C, an application to RtMidi

Question

I\'ve read several of the previous discussion about the subject but since I\'m relatively new to Objective-C, I don\'t really understand them. (Blocks, selectors, and delega

Answer 1

It's possible to have C++ and Objective-C within the same project and even within the same file (Objective-C++ with file extension .mm). If the code you're using is designed for a C++ callback, it may be easier to provide that and communicate between different object types outside of that mechanism.

---

//  CPPClass.h

#ifndef CPPClass_h
#define CPPClass_h

class CPPClass {
private:
    id m_ocObject;

public:
    CPPClass(id ocObject);
    virtual ~CPPClass();

    void verifyCPP();

};

#endif

---

//  OCClass.h

#import 

class CPPClass;

@interface OCClass : NSObject {
    CPPClass *cppObject;
}

- (void)ocCallback;
- (void)verifyOC;

@end

---

//  OCClass.mm

#import "OCClass.h"
#import "CPPClass.h"

#include 

@implementation OCClass

- (id)init {
    self = [super init];
    if (self) {
        cppObject = new CPPClass(self);
    }
    return self;
}

- (void)dealloc {
    delete cppObject;
}

- (void)ocCallback {
    NSLog(@"Objective-C called from C++");
}

- (void)verifyOC {
    NSLog(@"Objective-C called from Objective-C");
    cppObject->verifyCPP();
}

@end

CPPClass::CPPClass(id ocObject) : m_ocObject(ocObject)
{}

CPPClass::~CPPClass() {}

void CPPClass::verifyCPP() {
    std::cout << "C++ called from Objective-C" << std::endl;
    [m_ocObject ocCallback];
}

To activate this, some other .mm file would have:

#import "OCClass.h"
...
OCClass *test = [[OCClass alloc] init];
[test verifyOC];