heap2.m

// gcc -o heap2 heap2.m -framework Foundation && ./heap2
#import <Foundation/Foundation.h>

CFTypeRef JBBRetainCallBack(CFAllocatorRef allocator, const void *obj) {
    return [(id)obj retain];
}

void JBBReleaseCallBack(CFAllocatorRef allocator, const void *obj) {
    [(id)obj release];
}

CFComparisonResult JBBCompareCallBack(const void *lhs, const void *rhs, void *info) {
    return [(id)lhs compare:(id)rhs];
}

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    CFBinaryHeapCallBacks ourCallbacks = {
        .version = 0,
        .copyDescription = CFCopyDescription,
        .retain = JBBRetainCallBack,
        .release = JBBReleaseCallBack,
        .compare = JBBCompareCallBack,
    };

    CFBinaryHeapRef heap = CFBinaryHeapCreate(NULL, 0, &ourCallbacks, NULL);
    CFBinaryHeapAddValue(heap, CFSTR("Jane"));
    CFBinaryHeapAddValue(heap, @"Joe");

    id minValue = nil;
    BOOL hasMin = CFBinaryHeapGetMinimumIfPresent(heap, (const void **)&minValue);
    [minValue retain];

    NSLog(@"hasMin = %i, minValue = %@", hasMin, minValue);

    [minValue release];
    CFShow(heap);
    CFRelease(heap);
    
    [pool drain];
    return 0;
}