BUG: NSFormatter in Java

[Benjamin Riefenstahl]

Hi all,


Benjamin Riefenstahl <benny@crocodial.de> writes:
> In a nutshell we try to use custom NSFormatter subclasses as the
> "formatter" parameter to the WOTextField component. This works fine for
> the formatting part, but the parsing part seems to be severely broken.
> It looks like the Java/ObjC bridge code does not work at all.
>
> [...]
>
> - Somebody on this list comes up with some ObjC trickery to correct the
> problem without looking at the source code.

I did bite the bullet today and implemented this myself.  I would like
to present the solution here for others to copy and for general
review.

I have two questions:

- I implemented the method objectValueForString: in the base class
  (just throwing an exception) because otherwise I got warnings from
  the compiler.  Is it considered better style to do it this way or is
  it better to live with the warnings and have slightly smaller code?

- I didn't implement exception handling in getObjectValue:.  As I
  understand the docs I should catch the Java exception
  NSFormatter.ParsingException and return NO from getObjectValue:.

  OTOH it's not clear to me what difference this would/should make.
  If, for testing, I just return NO from my method than the
  WOTextField component just ignores any change to the value silently,
  leaving the old value.  But I do not consider that usefull behaviour
  because it basically prevents detection of the error in the
  application or component.

  I notice that the documentation for the ObjC version of the class
  talks about catching errors in NSControl, but that doesn't apply to
  a WOF application, does it?  And it's not mentioned in the Java docs
  either.

  On the whole I think I prefer all exceptions to be passed up and the
  ObjC error handling just be ignored.  Am I missing anything?


Ok, enough of that, here is the code.  Note: This is my first ObjC
class so please be gentle with me ;-).


>>>>>>>>>>>>> snip <<<<<<<<<<<<<<<<
/*------------------------------------------------------------------------
	NSFormatterPatch.h

	Fri 28-Jan-2000 Benny	Created
--------------------------------------------------------------------------
	$Log: .../NSFormatterPatch.h $
	
	1     00-01-28 16:49 Benny
	Patch NSFormatter class to actually work with the documented Java
	interface
------------------------------------------------------------------------*/
/*------------------------------------------------------------------------
	imports
------------------------------------------------------------------------*/
#import <Foundation/NSFormatter.h>

/*------------------------------------------------------------------------
	class
------------------------------------------------------------------------*/
@interface NSFormatterPatch : NSFormatter
{
}

+ (void) load;

- (BOOL) getObjectValue: (id*) anObject
	      forString: (NSString*) string
       errorDescription: (NSString**) error;

- (id) objectValueForString: (NSString*) string;

@end

/*
Local Variables: ***
mode: objc ***
End: ***
*/

/*------------------------------------------------------------------------
				eof
------------------------------------------------------------------------*/
>>>>>>>>>>>>> snip <<<<<<<<<<<<<<<<
/*------------------------------------------------------------------------
	NSFormatterPatch.m

	Fri 28-Jan-2000 Benny	Created
--------------------------------------------------------------------------
	$Log: .../NSFormatterPatch.m $
	
	1     00-01-28 16:49 Benny
	Patch NSFormatter class to actually work with the documented Java
	interface
------------------------------------------------------------------------*/
/*------------------------------------------------------------------------
	imports
------------------------------------------------------------------------*/
#import <Foundation/NSString.h>
#import <Foundation/NSException.h>

#import "NSFormatterPatch.h"

/*------------------------------------------------------------------------
	class
------------------------------------------------------------------------*/
@implementation NSFormatterPatch

+ (void) load
{
	[NSFormatterPatch poseAsClass: [NSFormatter class]];
}

- (BOOL) getObjectValue: (id*) anObject
	      forString: (NSString*) string
       errorDescription: (NSString**) error
{
	*anObject = [self objectValueForString: string];
	return YES;
}

- (id) objectValueForString:
	(NSString*) string
{
	[[NSException
		 exceptionWithName: @"objectValueForString not implemented"
		 reason: @"Must override objectValueForString in Java class"
		 userInfo: nil
		] raise]
		;
	return nil;
}

@end

/*------------------------------------------------------------------------
				eof
------------------------------------------------------------------------*/
>>>>>>>>>>>>> snip <<<<<<<<<<<<<<<<


so long, benny
======================================
Benjamin Riefenstahl (benny@crocodial.de)
ISION Internet AG
Ruhrstr. 61, D-22761 Hamburg, Germany