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42 lines
756 B
42 lines
756 B
6 years ago
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/*
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* Copyright (c) 2018-present, Facebook, Inc.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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#import <Foundation/Foundation.h>
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@interface A : NSObject
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@end
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@implementation A
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+ (instancetype)sharedInstanceOK {
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static id _sharedInstance = nil;
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static dispatch_once_t onceTokenA;
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dispatch_once(&onceTokenA, ^{
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_sharedInstance = [[self alloc] init];
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});
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return _sharedInstance;
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}
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@end
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@interface B : NSObject
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@end
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@implementation B
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+ (instancetype)sharedInstanceBAD {
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static id _sharedInstance = nil;
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dispatch_once_t onceTokenB;
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dispatch_once(&onceTokenB, ^{
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_sharedInstance = [[self alloc] init];
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});
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return _sharedInstance;
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}
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@end
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