No callback when clicking a menu item

I am trying to implement a simple context menu in my FinderSync extension.

I built the following using some examples and my problem is that the callback is never called when I click a menu item.

Source:

ContextMenuHelper.h

#import <Foundation/Foundation.h>
#include "FinderSync.h"

@interface ContextMenuHelper : NSObject

+ (NSMenu *)buildMenu;

@end

      

        
        
        
      

    

ContextMenuHelper.m

#import "ContextMenuHelper.h"

#define SharedContextMenuTarget  [ContextMenuTarget sharedInstance]

@interface ContextMenuTarget : NSObject
+ (ContextMenuTarget *) sharedInstance;
@end

@implementation ContextMenuTarget

- (void) callback              : (id)sender {
    NSLog(@"Called back!!!");
}

+ (ContextMenuTarget *) sharedInstance
{
    static ContextMenuTarget *sharedContextMenuTarget = nil;
    @synchronized(self)
    {
        if (!sharedContextMenuTarget)
            sharedContextMenuTarget = [[ContextMenuTarget alloc] init];
        return sharedContextMenuTarget;
    }
}

@end

@implementation ContextMenuHelper

+ (NSMenu *)buildMenu
{
    ContextMenuTarget *contextMenuTarget = SharedContextMenuTarget;

    NSMenu *mySubmenu = [[NSMenu alloc] initWithTitle:@""];

    NSMenuItem *newMenu = [[NSMenuItem alloc] initWithTitle:@"hello"
                                                     action:@selector(callback:)
                                              keyEquivalent:@""];
    [newMenu setTarget:contextMenuTarget];
    [mySubmenu addItem:newMenu];

    return mySubmenu;
}

@end

      

        
        
        
      

    

MyFinderSync.m

...
- (NSMenu *)menuForMenuKind:(FIMenuKind)whichMenu {

    NSMenu *myContextMenu = [[NSMenu alloc] initWithTitle:@""];

    @try
    {
        if(whichMenu != FIMenuKindContextualMenuForItems) {
            return myContextMenu;
        }

        myContextMenu = [ContextMenuHelper buildMenu];
    }
    @catch (NSException *ex)
    {
    }

    return myContextMenu;
}
...