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122 lines
2.1 KiB
Objective-C
122 lines
2.1 KiB
Objective-C
/** Implementation for NSNull for GNUStep
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Copyright (C) 2000 Free Software Foundation, Inc.
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Written by: Richard Frith-Macdonald <rfm@gnu.org>
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Date: 2000
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This file is part of the GNUstep Base Library.
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free
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Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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Boston, MA 02110 USA.
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<title>NSNull class reference</title>
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*/
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#import "common.h"
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#import "Foundation/NSNull.h"
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/**
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* An object to use as a placeholder - in collections for instance.
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*/
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@implementation NSNull
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static NSNull *null = 0;
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+ (id) allocWithZone: (NSZone*)z
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{
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return null;
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}
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+ (id) alloc
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{
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return null;
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}
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+ (void) initialize
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{
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if (null == 0)
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{
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null = (NSNull*)NSAllocateObject(self, 0, NSDefaultMallocZone());
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[[NSObject leakAt: &null] release];
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}
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}
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/**
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* Return an object that can be used as a placeholder in a collection.
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* This method always returns the same object.
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*/
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+ (NSNull*) null
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{
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return null;
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}
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- (id) autorelease
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{
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return self;
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}
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- (id) copyWithZone: (NSZone*)z
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{
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return self;
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}
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- (id) copy
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{
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return self;
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}
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- (void) dealloc
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{
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GSNOSUPERDEALLOC;
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}
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- (NSString*) description
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{
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return @"<null>";
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}
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- (id) valueForUndefinedKey: (NSString*)aKey
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{
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return null;
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}
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- (void) encodeWithCoder: (NSCoder*)aCoder
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{
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}
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- (id) initWithCoder: (NSCoder*)aCoder
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{
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return self;
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}
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- (BOOL) isEqual: (id)other
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{
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if (other == self)
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return YES;
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else
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return NO;
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}
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- (oneway void) release
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{
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}
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- (id) retain
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{
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return self;
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}
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@end
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