Objective-C++: Is there any way to vend a C++ object?

Question

I am making heavy use of Objective-C++. I know that while I can include C++ code in my Objective-C code, the converse is not true. I'd like to vend a custom C++ object I have created, to my Objective-C process through a distributed object. When I try to do this, I get the following error message:

error: cannot convert ‘custom_class*’ to ‘objc_object*’ in argument passing

Is there any way to vend a custom C++ object, to another Objective-C process?

The code I have:

#import <Cocoa/Cocoa.h>
#import <iostream>
#import <stdio.h>

using namespace std;

class custom_class {
    public:
    custom_class();
    ~custom_class();
    void hello();
};

custom_class::custom_class() { }
custom_class::~custom_class() { }
void custom_class::hello() { cout << "Hello World!" << endl; }

int main() {
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

    cout << "Starting vendor " << endl;

    custom_class *test = new custom_class();

    NSConnection *connection = [NSConnection connectionWithReceivePort:[NSPort port] sendPort:nil];
    [connection setRequestTimeout:1];
    [connection setRootObject:test];
    [connection registerName:@"DisObjTest"];

    [[NSRunLoop currentRunLoop] run];

    [pool drain];

    return 0;
}

You may be interested in this question: http://stackoverflow.com/questions/10014684/objective-c-disadvantages-to-bridging-with-c — Richard J. Ross III, Aug 29 '12 at 13:00

score 4 · Accepted Answer · answered Jul 19 '12 at 20:45

4

This cannot be done without wrapping the C++ class in an Objective-C class. All the runtime machinery that makes distributed objects possible is not available in C++.

answered Jul 19 '12 at 20:45

Sven

22,475
4
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That's what I assumed. However, as far as I know, I cannot include Obj-C in my C++ code. That is the issue I'm having at the moment. – Julio Jul 19 '12 at 20:46
1

You can if you compile it as Objective-C++ – Sven Jul 19 '12 at 20:49

score -1 · Answer 2 · answered Jul 19 '12 at 20:45

-1

Wrap it inside a objective-C interface:

class custom_class;
@interface custom_class_wrapper : NSObject
@propery (nonatomic, assign) custom_class* obj;
@end

Or inside an NSValue, this requires casts though

custom_class a;
id obj = [NSValue valueWithPointer:&a];
custom_class* a_val = static_cast<custom_class*>([obj pointerValue]);

answered Jul 19 '12 at 20:45

Hampus Nilsson

6,692
1
25
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That will get the pointer value over to the other process where it will be useless. – Sven Jul 19 '12 at 20:48

Objective-C++: Is there any way to vend a C++ object?

2 Answers2