Need help understanding subclassing issue

[Pierre Bz]

I am having problems with writing a subclass.
I wrote a simplified (trivial) subclass of NSDictionary
and it fails.  I need help understanding why.
I've attempted include all necessary information in this post
so someone knowledgeable has the information he needs to
offer a suggestion.

TIA


test result:
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2009-02-19 16:17:21.760 testcase[12478] testDictionary {Key = Val; }
2009-02-19 16:17:21.766 testcase[12478] This exception was raised: 
<NSException: 0x811dd70> NAME:NSGenericException 
REASON:subclass OGBanner(instance) should override count

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

testcase.m:
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#import <Foundation/Foundation.h>
#import "banner.h"
int main( void )
{
  /*
   * This is a reduced test to illustrate my problem.
   * OGBanner is a subclass of NSDictionary.
   * It does nothing except for being a new name for NSDictionary.
   * Yet it fails to work.
   *
   * When I got the exception message, I added the implementation
   * of count in banner.m and banner.h, but to no avail.
   */
  NSAutoreleasePool * pool;
  NSDictionary * testDictionary;
  OGBanner * testBanner;
  NSString * key = @"Key";
  NSString * val = @"Val";
  pool = [NSAutoreleasePool new];

  testBanner = [[OGBanner alloc] initWithObjects: &val forKeys: &key count: 1];
  testDictionary = [[NSDictionary alloc] initWithObjects: & val 
                                         forKeys: & key count: 1];
  NSLog(  @"testDictionary %@", testDictionary ); /* This works */
  NS_DURING
    {
      NSLog(  @"testBanner %@", testBanner ); /* This does not work */
    }
  NS_HANDLER
    {
      NSLog( @"This exception was raised: %@", localException );
    }
  NS_ENDHANDLER; 
  return EXIT_SUCCESS ;
}
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

banner.h:
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#import <Foundation/Foundation.h>

@interface OGBanner : NSDictionary
{
}

- (id) initWithObjects: (id *) objects 
  forKeys: (id *) keys count: (unsigned ) count;
- (unsigned) count;
@end


^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
banner.m:
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#import <Foundation/Foundation.h>
#import "banner.h"

@implementation OGBanner : NSDictionary

- (id) initWithObjects: (id *) objects 
                        forKeys: (id *) keys 
                        count: (unsigned) count
{
  return [super initWithObjects: objects forKeys: keys count: count];
}

- (unsigned) count
{
  return [super count];
}

@end;

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

GNUmakefile
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include $(GNUSTEP_MAKEFILES)/common.make

TOOL_NAME = testcase

testcase_HEADERS = banner.h 
testcase_OBJC_FILES = testcase.m banner.m 
testcase_RESOURCE_FILES =

include $(GNUSTEP_MAKEFILES)/tool.make

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Details of the development environment
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Work bench information
    GNUSTEP_HOST_CPU = ix86
    GNUSTEP_HOST_OS = linux-gnu
    MAKE_VERSION = GNU Make 3.81
    GCC_VERSION = gcc (GCC) 4.2.4 (Ubuntu 4.2.4-1ubuntu3)
    LIBRARY_COMBO = gnu-gnu-gnu
    KERNEL_NAME = Linux
    KERNEL_RELEASE = 2.6.24-23-generic
    KERNEL_VERSION = #1 SMP Mon Jan 26 00:13:11 UTC 2009
    MACHINE = i686
    arguments = (obj/benchinfo)
    globallyUniqueString = homard_2d8f_f4dfe20_0
    processName = benchinfo
    hostName = homard
    operatingSystemName = GSGNULinuxOperatingSystem
    operatingSystemVersionString = 2.6.24-23-generic
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^