NSValue C++ object

NSValue+CVMat.h

#import <Foundation/Foundation.h>

namespace cv {
    class Mat;
}

@interface NSValue (CVMat)

+ (instancetype)valueWithCVMat:(cv::Mat)mat;
@property (readonly) cv::Mat CVMatValue;

@end

NSValue+CVMat.mm

#import <opencv2/opencv.hpp>
#import "NSValue+CVMat.h"

@interface NSValueDeleteOnDealloc : NSValue

@property (strong, nonatomic) NSValue *value;

@end

@implementation NSValueDeleteOnDealloc

- (void)dealloc {
    delete self.value.pointerValue;
}

- (BOOL)respondsToSelector:(SEL)aSelector {
    return [super respondsToSelector:aSelector]
        || [self.value respondsToSelector:aSelector];
}

- (id)forwardingTargetForSelector:(SEL)aSelector {
    return self.value;
}

@end

//

@implementation NSValue (CVMat)

+ (instancetype)valueWithCVMat:(cv::Mat)mat {
    NSValueDeleteOnDealloc *me = [[NSValueDeleteOnDealloc alloc] init];
    me.value = [NSValue valueWithPointer:(new cv::Mat(mat))];
    return me;
}

- (cv::Mat)CVMatValue {
    if ([self isKindOfClass:[NSValueDeleteOnDealloc class]]) {
        NSValueDeleteOnDealloc *me = self;
        return *(cv::Mat *)me.value.pointerValue;
    }
    return cv::Mat();
}

@end