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//
// GTMObjectSingleton.h
// Macro to implement methods for a singleton
//
// Copyright 2005-2008 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy
// of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
//
#import "GTMDefines.h"
/// This macro implements the various methods needed to make a safe singleton.
//
/// This Singleton pattern was taken from:
/// http://developer.apple.com/documentation/Cocoa/Conceptual/CocoaFundamentals/CocoaObjects/chapter_3_section_10.html
///
/// Sample usage:
///
/// GTMOBJECT_SINGLETON_BOILERPLATE(SomeUsefulManager, sharedSomeUsefulManager)
/// (with no trailing semicolon)
///
#define GTMOBJECT_SINGLETON_BOILERPLATE(_object_name_, _shared_obj_name_) \
static _object_name_ *z##_shared_obj_name_ = nil; \
+ (_object_name_ *)_shared_obj_name_ { \
@synchronized(self) { \
if (z##_shared_obj_name_ == nil) { \
/* Note that 'self' may not be the same as _object_name_ */ \
/* first assignment done in allocWithZone but we must reassign in case init fails */ \
z##_shared_obj_name_ = [[self alloc] init]; \
_GTMDevAssert((z##_shared_obj_name_ != nil), @"didn't catch singleton allocation"); \
} \
} \
return z##_shared_obj_name_; \
} \
+ (id)allocWithZone:(NSZone *)zone { \
@synchronized(self) { \
if (z##_shared_obj_name_ == nil) { \
z##_shared_obj_name_ = [super allocWithZone:zone]; \
return z##_shared_obj_name_; \
} \
} \
\
/* We can't return the shared instance, because it's been init'd */ \
_GTMDevAssert(NO, @"use the singleton API, not alloc+init"); \
return nil; \
} \
- (id)retain { \
return self; \
} \
- (NSUInteger)retainCount { \
return NSUIntegerMax; \
} \
- (void)release { \
} \
- (id)autorelease { \
return self; \
} \
- (id)copyWithZone:(NSZone *)zone { \
return self; \
} \
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