单例设计模式

// 以后就可以使用interfaceSingleton来替代后面的方法声明
#define interfaceSingleton(name)  +(instancetype)share##name


#if __has_feature(objc_arc)
// ARC
#define implementationSingleton(name)  + (instancetype)share##name { name *instance = [[self alloc] init]; return instance; } static name *_instance = nil; + (instancetype)allocWithZone:(struct _NSZone *)zone { static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ _instance = [[super allocWithZone:zone] init]; }); return _instance; } - (id)copyWithZone:(NSZone *)zone{ return _instance; } - (id)mutableCopyWithZone:(NSZone *)zone { return _instance; }
#else
// MRC

#define implementationSingleton(name)  + (instancetype)share##name { name *instance = [[self alloc] init]; return instance; } static name *_instance = nil; + (instancetype)allocWithZone:(struct _NSZone *)zone { static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ _instance = [[super allocWithZone:zone] init]; }); return _instance; } - (id)copyWithZone:(NSZone *)zone{ return _instance; } - (id)mutableCopyWithZone:(NSZone *)zone { return _instance; } - (oneway void)release { } - (instancetype)retain { return _instance; } - (NSUInteger)retainCount { return  MAXFLOAT; }
#endif

//
//  Person.h


#import <Foundation/Foundation.h>
#import "Singleton.h"

@interface Person : NSObject

interfaceSingleton(Person);

@end

//
//  Person.m



#import "Person.h"

@implementation Person


implementationSingleton(Person)

@end