//Singleton.h// 以后就可以使用interfaceSingleton来替代后面的方法声明。    \表示下一行也是上一行的内容。#define interfaceSingleton(name)  +(instancetype)share##name#if __has_feature(objc_arc)//ARC编译这段#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,编译这段。#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

////  Tools.h#import 
     
      #import "Singleton.h"@interface Tools : NSObject
      
       // share + 当前的类名//+ (instancetype)shareTools;interfaceSingleton(Tools);  ////用Singleton.h里面的内容替换。@end
      
     

////  Tools.m#import "Tools.h"@implementation Tools/*+ (instancetype)shareTools{    Tools *instance = [[self alloc] init];    return instance;}static Tools *_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;}// MRC- (oneway void)release{}- (instancetype)retain{    return _instance;}- (NSUInteger)retainCount{    return  MAXFLOAT;}*/implementationSingleton(Tools)   ////用Singleton.h里面的内容替换。@end

////  Person.h//#import 
     
      #import "Singleton.h"@interface Person : NSObjectinterfaceSingleton(Person);   ////用Singleton.h里面的内容替换。@end
     

////  Person.m#import "Person.h"@implementation PersonimplementationSingleton(Person)    //用Singleton.h里面的内容替换。@end

////  main.m//  宏定义抽取单例，宏定义本质是替换，简化代码，用公用的代码进行替换。//#import 
     
      #import "Tools.h"#import "Person.h"int main(int argc, const char * argv[]) {        Tools *t1 = [[Tools alloc] init]; //内部会调用allocWithZone    Tools *t2 = [Tools new];// [[alloc] init]  allocWithZone    Tools *t3 = [Tools shareTools];        Tools *t4 = [t3 copy];    Tools *t5 = [t3 mutableCopy];        NSLog(@"%p, %p, %p, %p, %p", t1, t2, t3, t4, t5);//0x100300120, 0x100300120, 0x100300120, 0x100300120, 0x100300120        Person *p1 = [Person sharePerson];    Person *p2 = [Person sharePerson];    Person *p3 = [Person sharePerson];        NSLog(@"%p, %p, %p", p1 , p2, p3);//0x100202460, 0x100202460, 0x100202460            // 如何判断当前是ARC还是MRC?    // 可以在编译的时候判断当前是否是ARC    #if __has_feature(objc_arc)        NSLog(@"ARC");    #else        NSLog(@"MRC");    #endif    return 0;}