iOS 计算起始时间和终止时间的差

简单的就是说 a = 终止 - 起始
求大神 帮忙解答,
求代码演示;

我是这样算的

• (void)viewDidAppear:(BOOL)animated
  {

  NSDateFormatter *formatter =[[NSDateFormatter alloc] init];
  [formatter setDateFormat:@"yyyy-MM-dd-HH-mm-ss"];
  self.currentTime = [formatter stringFromDate:[NSDate date]];
  NSLog(@"DATE = %@", [NSDate date]);

  NSLog(@"ooooo%@", self.currentTime);

}

• (void)viewWillDisappear:(BOOL)animated { NSDateFormatter *date=[[NSDateFormatter alloc] init]; [date setDateFormat:@"yyyy-MM-dd HH:mm:ss"]; NSString *currentEndTime = [date stringFromDate:[NSDate date]]; NSCalendar *cal=[NSCalendar currentCalendar]; unsigned int unitFlags= NSYearCalendarUnit| NSMonthCalendarUnit| NSDayCalendarUnit|NSHourCalendarUnit|NSMinuteCalendarUnit|NSSecondCalendarUnit; NSDateComponents *d = [cal components:unitFlags fromDate:self.currentTime toDate:currentEndTime options:0]; NSLog(@"%d天%d小时%d分钟%d秒",[d day],[d hour],[d minute],[d second]);

}

打印

015-04-27 13:47:36.082 H_J_4[30420:576015] -[__NSCFString timeIntervalSinceReferenceDate]: unrecognized selector sent to instance 0x7fd6c144ebd0
(lldb)

ios计算时间差 转
//模拟windows下 GetTickCount //
//#import

• (int)mxGetTickCount;
  {
  int timeTick;
  mach_timebase_info_data_t info;
  uint64_t machineTime;
  mach_timebase_info(&info);
  machineTime =mach_absolute_time();
  timeTick = machineTime * info.numer / info.denom /1000000LL;

  return timeTick;
  }

// NSDate timeIntervalSinceDate:

//下面转换NSString，用在保存时间时使用。

• (double)GetStringTimeDiff:(NSString*)timeS timeE:(NSString*)timeE

{

double timeDiff = 0.0;

NSDateFormatter *formatters = [[NSDateFormatter alloc] init];
[formatters setDateFormat:@"yyyy/MM/dd HH:mm:ss:SSS"];
NSDate *dateS = [formatters dateFromString:timeS];



NSDateFormatter *formatterE = [[NSDateFormatter alloc] init];
[formatterE setDateFormat:@"yyyy/MM/dd HH:mm:ss:SSS"];
NSDate *dateE = [formatterE dateFromString:timeE];


timeDiff = [dateE timeIntervalSinceDate:dateS ];

return timeDiff;

}

• (NSString*)GetCurTime

{

NSDateFormatter *formatter = [[NSDateFormatter alloc] init];

[formatter setDateFormat:@"yyyy/MM/dd HH:mm:ss:SSS"];

NSString*timeString=[formatter stringFromDate: [NSDate date]];

[formatter release];

return timeString;

}