1 #import <Foundation/Foundation.h>2 3 @interface SoundTool : NSObject <NSCopying>4 5 + (instancetype)shareSoundTool;6 7 @end

#import "SoundTool.h"@implementation SoundToolstatic id _instance = nil;+ (instancetype)allocWithZone:(struct _NSZone *)zone{    if (_instance == nil) {        static dispatch_once_t onceToken;        dispatch_once(&onceToken, ^{            _instance = [super allocWithZone:zone];        });    }    return _instance;}+ (instancetype)shareSoundTool{    return [[self alloc] init];}- (instancetype)init{    static dispatch_once_t onceToken;    dispatch_once(&onceToken, ^{        _instance = [super init];    });    return _instance;}+ (instancetype)copyWithZone:(struct _NSZone *)zone{    return _instance;}+ (instancetype)mutableCopyWithZone:(struct _NSZone *)zone{    return _instance;}//以下三個為非ARC使用- (oneway void)release{}- (instancetype)retain{    return _instance;}- (NSUInteger)retainCount{    return 1;}