判断是否在某个时间戳之前

//判断是否是多少秒前

• (BOOL)isBefore:(NSString *)dateString gap:(NSTimeInterval)timeInterval
  {
  NSDate *date = [NSDate dateWithTimeIntervalSince1970:[dateString doubleValue]/1000];
  return [self isBeforeWithDate:date gap:timeInterval];
  }

• (BOOL)isBeforeWithDate:(NSDate *)date gap:(NSTimeInterval)timeInterval
  {
  NSDate *tenMinut = [NSDate dateWithTimeIntervalSinceNow:timeInterval];

  NSComparisonResult result = [date compare:tenMinut];
  if (result == NSOrderedDescending) {
  return NO;
  }
  return YES;
  }