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88 lines
2.0 KiB
Plaintext
88 lines
2.0 KiB
Plaintext
/*
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* CPNull.j
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* Foundation
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*
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* Created by Francisco Tolmasky.
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* Copyright 2008, 280 North, Inc.
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*
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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 2.1 of the License, or (at your option) any later version.
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*
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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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*
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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 Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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@import "CPObject.j"
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var CPNullSharedNull = nil;
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/*!
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@class CPNull
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@ingroup foundation
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@brief An object representation of \c nil.
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This class is used as an object representation of \c nil. This is handy when a collection
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only accepts objects as values, but you would like a \c nil representation in there.
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*/
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@implementation CPNull : CPObject
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{
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}
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/*+ (id)alloc
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{
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if (CPNullSharedNull)
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return CPNullSharedNull;
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return [super alloc];
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}*/
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/*!
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Returns the singleton instance of the CPNull
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object. While CPNull and \c nil should
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be <i>interpreted</i> as the same, they are not equal ('==').
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*/
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+ (CPNull)null
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{
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if (!CPNullSharedNull)
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CPNullSharedNull = [[CPNull alloc] init];
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return CPNullSharedNull;
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}
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- (BOOL)isEqual:(id)anObject
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{
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if (self === anObject)
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return YES;
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return [anObject isKindOfClass:[CPNull class]];
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}
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/*!
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Returns CPNull null.
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@param aCoder the coder from which to do nothing
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@return [CPNull null]
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*/
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- (id)initWithCoder:(CPCoder)aCoder
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{
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return [CPNull null];
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}
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/*!
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Writes out nothing to the specified coder.
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@param aCoder the coder to which nothing will
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be written
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*/
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- (void)encodeWithCoder:(CPCoder)aCoder
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{
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}
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@end
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