HMDataTool.h#import 
     
      @interface HMDataTool : NSObject+ (instancetype)sharedDataTool;@endHMDataTool.m#import "HMDataTool.h"@implementation HMDataTool// 用来保存唯一的单例对象static id _instace;+ (id)allocWithZone:(struct _NSZone *)zone{    static dispatch_once_t onceToken;    dispatch_once(&onceToken, ^{        _instace = [super allocWithZone:zone];    });    return _instace;}+ (instancetype)sharedDataTool{    static dispatch_once_t onceToken;    dispatch_once(&onceToken, ^{        _instace = [[self alloc] init];    });    return _instace;}- (id)copyWithZone:(NSZone *)zone{    return _instace;}- (oneway void)release { }- (id)retain { return self; }- (NSUInteger)retainCount { return 1;}- (id)autorelease { return self;}@end