/* Interface for NSValueTransformer for GNUStep
   Copyright (C) 2006 Free Software Foundation, Inc.

   Written Dr. H. Nikolaus Schaller
   Created on Mon Mar 21 2005.
   Updatesd and documented by Richard Frith-Macdonald
   
   This file is part of the GNUstep Base Library.

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 3 of the License, or (at your option) any later version.
   
   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.
   
   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, write to the Free
   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
   Boston, MA 02111 USA.
   */ 

#ifndef __NSValueTransformer_h_GNUSTEP_BASE_INCLUDE
#define __NSValueTransformer_h_GNUSTEP_BASE_INCLUDE
#import	<GNUstepBase/GSVersionMacros.h>

#if OS_API_VERSION(100300,GS_API_LATEST) && GS_API_VERSION(010200,GS_API_LATEST)

#import	<Foundation/NSObject.h>

#if	defined(__cplusplus)
extern "C" {
#endif

@class NSArray;
@class NSString;

/** This transformer converts a YES to a NO and a NO to a YES.
 */
GS_EXPORT NSString* const NSNegateBooleanTransformerName;

/** This transformer converts a nil value to a YES.<br />
 * Not reversible.
 */
GS_EXPORT NSString* const NSIsNilTransformerName;

/** This transformer converts a non-nil value to a YES.<br />
 * Not reversible.
 */
GS_EXPORT NSString* const NSIsNotNilTransformerName; 

/** This transformer converts an [NSData] instance to the object
 * archived in it, or archives an object inot an [NSData].
 */
GS_EXPORT NSString* const NSUnarchiveFromDataTransformerName;

/** Instances of the NSValueTransformer class are used to convert
 * values from one representation to another.  The base class is
 * abstract and its methods must be overridden by subclasses to do
 * the actual work.
 */
@interface NSValueTransformer : NSObject

/** <override-subclass />
 * Returns a flag indicating whether the transformer permits reverse
 * transformations.
 */
+ (BOOL) allowsReverseTransformation;

/**
 * Registers transformer to handle transformations with the specified
 * name.
 */
+ (void) setValueTransformer: (NSValueTransformer *)transformer
		     forName: (NSString *)name;

/** <override-subclass />
 * Returns the class of the value produced by this transformer.
 */
+ (Class) transformedValueClass;

/**
 * Returns the transformer registered for the specified name, or nil
 * if no transformer is registered for name.
 */
+ (NSValueTransformer *) valueTransformerForName: (NSString *)name;

/**
 * Returns an array listing the names of all registered value transformers.
 */
+ (NSArray *) valueTransformerNames;

/**
 * Performs a reverse transformation on the specified value and returns the
 * resulting object.<br />
 * The default implementation raises an exception if
 * +allowsReverseTransformation returns NO, otherwise it calls
 * -transformedValue: and returns the result.
 */
- (id) reverseTransformedValue: (id)value;

/** <override-subclass/>
 * Subclasses should override this method to perform the actual transformation
 * (and reverse transformation if applicable) and return the result.
 */
- (id) transformedValue: (id)value;

@end

#if	defined(__cplusplus)
}
#endif

#endif	/* OS_API_VERSION */

#endif /* __NSValueTransformer_h_GNUSTEP_BASE_INCLUDE */
