import “Date.h”

@implementation NSDate(Helpers)

//获取年月日如:19871127.
- (NSString *)getFormatYearMonthDay
{
NSString *string = [NSString stringWithFormat:@”%d%02d%02d”,[self getYear],[self getMonth],[self getDay]];
return string;
}

//该日期是该年的第几周
- (int )getWeekOfYear
{
int i;
int year = [self getYear];
NSDate *date = [self endOfWeek];
for (i = 1;[[date dateAfterDay:-7 * i] getYear] == year;i++)
{
}
return i;
}
//返回day天后的日期(若day为负数,则为|day|天前的日期)
- (NSDate *)dateAfterDay:(int)day
{
NSCalendar *calendar = [NSCalendar currentCalendar];
// Get the weekday component of the current date
// NSDateComponents *weekdayComponents = [calendar components:NSWeekdayCalendarUnit fromDate:self];
NSDateComponents *componentsToAdd = [[NSDateComponents alloc] init];
// to get the end of week for a particular date, add (7 - weekday) days
[componentsToAdd setDay:day];
NSDate *dateAfterDay = [calendar dateByAddingComponents:componentsToAdd toDate:self options:0];
[componentsToAdd release];

return dateAfterDay;

}
//month个月后的日期
- (NSDate *)dateafterMonth:(int)month
{
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *componentsToAdd = [[NSDateComponents alloc] init];
[componentsToAdd setMonth:month];
NSDate *dateAfterMonth = [calendar dateByAddingComponents:componentsToAdd toDate:self options:0];
[componentsToAdd release];

return dateAfterMonth;

}
//获取日
- (NSUInteger)getDay{
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *dayComponents = [calendar components:(NSDayCalendarUnit) fromDate:self];
return [dayComponents day];
}
//获取月
- (NSUInteger)getMonth
{
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *dayComponents = [calendar components:(NSMonthCalendarUnit) fromDate:self];
return [dayComponents month];
}
//获取年
- (NSUInteger)getYear
{
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *dayComponents = [calendar components:(NSYearCalendarUnit) fromDate:self];
return [dayComponents year];
}
//获取小时
- (int )getHour {
NSCalendar *calendar = [NSCalendar currentCalendar];
NSUInteger unitFlags =NSYearCalendarUnit| NSMonthCalendarUnit | NSDayCalendarUnit |NSHourCalendarUnit|NSMinuteCalendarUnit;
NSDateComponents *components = [calendar components:unitFlags fromDate:self];
NSInteger hour = [components hour];
return (int)hour;
}
//获取分钟
- (int)getMinute {
NSCalendar *calendar = [NSCalendar currentCalendar];
NSUInteger unitFlags =NSYearCalendarUnit| NSMonthCalendarUnit | NSDayCalendarUnit |NSHourCalendarUnit|NSMinuteCalendarUnit;
NSDateComponents *components = [calendar components:unitFlags fromDate:self];
NSInteger minute = [components minute];
return (int)minute;
}
- (int )getHour:(NSDate *)date {
NSCalendar *calendar = [NSCalendar currentCalendar];
NSUInteger unitFlags =NSYearCalendarUnit| NSMonthCalendarUnit | NSDayCalendarUnit |NSHourCalendarUnit|NSMinuteCalendarUnit;
NSDateComponents *components = [calendar components:unitFlags fromDate:date];
NSInteger hour = [components hour];
return (int)hour;
}
- (int)getMinute:(NSDate *)date {
NSCalendar *calendar = [NSCalendar currentCalendar];
NSUInteger unitFlags =NSYearCalendarUnit| NSMonthCalendarUnit | NSDayCalendarUnit |NSHourCalendarUnit|NSMinuteCalendarUnit;
NSDateComponents *components = [calendar components:unitFlags fromDate:date];
NSInteger minute = [components minute];
return (int)minute;
}
//在当前日期前几天
- (NSUInteger)daysAgo {
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [calendar components:(NSDayCalendarUnit)
fromDate:self
toDate:[NSDate date]
options:0];
return [components day];
}
//午夜时间距今几天
- (NSUInteger)daysAgoAgainstMidnight {
// get a midnight version of ourself:
NSDateFormatter *mdf = [[NSDateFormatter alloc] init];
[mdf setDateFormat:@”yyyy-MM-dd”];
NSDate *midnight = [mdf dateFromString:[mdf stringFromDate:self]];
[mdf release];

return (int)[midnight timeIntervalSinceNow] / (60*60*24) *-1;

}

• (NSString *)stringDaysAgo {
  return [self stringDaysAgoAgainstMidnight:YES];
  }

• (NSString *)stringDaysAgoAgainstMidnight:(BOOL)flag {
  NSUInteger daysAgo = (flag) ? [self daysAgoAgainstMidnight] : [self daysAgo];
  NSString *text = nil;
  switch (daysAgo) {
  case 0:
  text = @”Today”;
  break;
  case 1:
  text = @”Yesterday”;
  break;
  default:
  text = [NSString stringWithFormat:@”%d days ago”, daysAgo];
  }
  return text;
  }

//返回一周的第几天(周末为第一天)
- (NSUInteger)weekday {
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *weekdayComponents = [calendar components:(NSWeekdayCalendarUnit) fromDate:self];
return [weekdayComponents weekday];
}
//转为NSString类型的
+ (NSDate )dateFromString:(NSString )string {
return [NSDate dateFromString:string withFormat:[NSDate dbFormatString]];
}

• (NSDate )dateFromString:(NSString )string withFormat:(NSString *)format {
  NSDateFormatter *inputFormatter = [[NSDateFormatter alloc] init];
  [inputFormatter setDateFormat:format];
  NSDate *date = [inputFormatter dateFromString:string];
  [inputFormatter release];
  return date;
  }

• (NSString )stringFromDate:(NSDate )date withFormat:(NSString *)format {
  return [date stringWithFormat:format];
  }

• (NSString )stringFromDate:(NSDate )date {
  return [date string];
  }

• (NSString )stringForDisplayFromDate:(NSDate )date prefixed:(BOOL)prefixed {
  /*

  • if the date is in today, display 12-hour time with meridian,
  • if it is within the last 7 days, display weekday name (Friday)
  • if within the calendar year, display as Jan 23
  • else display as Nov 11, 2008
    */

  NSDate *today = [NSDate date];
  NSCalendar *calendar = [NSCalendar currentCalendar];
  NSDateComponents *offsetComponents = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit |NSDayCalendarUnit)
  fromDate:today];

  NSDate *midnight = [calendar dateFromComponents:offsetComponents];

  NSDateFormatter *displayFormatter = [[NSDateFormatter alloc] init];
  NSString *displayString = nil;

  // comparing against midnight
  if ([date compare:midnight] == NSOrderedDescending) {
  if (prefixed) {
  [displayFormatter setDateFormat:@“‘at’ h:mm a”]; // at 11:30 am
  } else {
  [displayFormatter setDateFormat:@”h:mm a”]; // 11:30 am
  }
  } else {
  // check if date is within last 7 days
  NSDateComponents *componentsToSubtract = [[NSDateComponents alloc] init];
  [componentsToSubtract setDay:-7];
  NSDate *lastweek = [calendar dateByAddingComponents:componentsToSubtract toDate:today options:0];
  [componentsToSubtract release];
  if ([date compare:lastweek] == NSOrderedDescending) {
  [displayFormatter setDateFormat:@”EEEE”]; // Tuesday
  } else {
  // check if same calendar year
  NSInteger thisYear = [offsetComponents year];

      NSDateComponents *dateComponents = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit |NSDayCalendarUnit) 
                                                     fromDate:date];
      NSInteger thatYear = [dateComponents year];
      if (thatYear >= thisYear) {
          [displayFormatter setDateFormat:@"MMM d"];
      } else {
          [displayFormatter setDateFormat:@"MMM d, yyyy"];
      }
  }
  if (prefixed) {
      NSString *dateFormat = [displayFormatter dateFormat];
      NSString *prefix = @"‘on‘ ";
      [displayFormatter setDateFormat:[prefix stringByAppendingString:dateFormat]];
  }
  

  }

  // use display formatter to return formatted date string
  displayString = [displayFormatter stringFromDate:date];
  [displayFormatter release];
  return displayString;
  }

• (NSString )stringForDisplayFromDate:(NSDate )date {
  return [self stringForDisplayFromDate:date prefixed:NO];
  }

• (NSString )stringWithFormat:(NSString )format {
  NSDateFormatter *outputFormatter = [[NSDateFormatter alloc] init];
  [outputFormatter setDateFormat:format];
  NSString *timestamp_str = [outputFormatter stringFromDate:self];
  [outputFormatter release];
  return timestamp_str;
  }

• (NSString *)string {
  return [self stringWithFormat:[NSDate dbFormatString]];
  }

• (NSString *)stringWithDateStyle:(NSDateFormatterStyle)dateStyle timeStyle:(NSDateFormatterStyle)timeStyle {
  NSDateFormatter *outputFormatter = [[NSDateFormatter alloc] init];
  [outputFormatter setDateStyle:dateStyle];
  [outputFormatter setTimeStyle:timeStyle];
  NSString *outputString = [outputFormatter stringFromDate:self];
  [outputFormatter release];
  return outputString;
  }
  //返回周日的的开始时间

• (NSDate *)beginningOfWeek {
  // largely borrowed from “Date and Time Programming Guide for Cocoa”
  // we’ll use the default calendar and hope for the best

  NSCalendar *calendar = [NSCalendar currentCalendar];
  NSDate *beginningOfWeek = nil;
  BOOL ok = [calendar rangeOfUnit:NSWeekCalendarUnit startDate:&beginningOfWeek
  interval:NULL forDate:self];
  if (ok) {
  return beginningOfWeek;
  }

  // couldn’t calc via range, so try to grab Sunday, assuming gregorian style
  // Get the weekday component of the current date
  NSDateComponents *weekdayComponents = [calendar components:NSWeekdayCalendarUnit fromDate:self];

  /*
  Create a date components to represent the number of days to subtract from the current date.
  The weekday value for Sunday in the Gregorian calendar is 1, so subtract 1 from the number of days to subtract from the date in question. (If today’s Sunday, subtract 0 days.)
  */
  NSDateComponents *componentsToSubtract = [[NSDateComponents alloc] init];
  [componentsToSubtract setDay: 0 - ([weekdayComponents weekday] - 1)];
  beginningOfWeek = nil;
  beginningOfWeek = [calendar dateByAddingComponents:componentsToSubtract toDate:self options:0];
  [componentsToSubtract release];

  //normalize to midnight, extract the year, month, and day components and create a new date from those components.
  NSDateComponents *components = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit |NSDayCalendarUnit)
  fromDate:beginningOfWeek];
  return [calendar dateFromComponents:components];
  }
  //返回当前天的年月日.

• (NSDate *)beginningOfDay {
  NSCalendar *calendar = [NSCalendar currentCalendar];
  // Get the weekday component of the current date
  NSDateComponents *components = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit |NSDayCalendarUnit)
  fromDate:self];
  return [calendar dateFromComponents:components];
  }
  //返回该月的第一天
• (NSDate *)beginningOfMonth
  {
  return [self dateAfterDay:-[self getDay] + 1];
  }
  //该月的最后一天
• (NSDate *)endOfMonth
  {
  return [[[self beginningOfMonth] dateafterMonth:1] dateAfterDay:-1];
  }
  //返回当前周的周末

• (NSDate *)endOfWeek {
  NSCalendar *calendar = [NSCalendar currentCalendar];
  // Get the weekday component of the current date
  NSDateComponents *weekdayComponents = [calendar components:NSWeekdayCalendarUnit fromDate:self];
  NSDateComponents *componentsToAdd = [[NSDateComponents alloc] init];
  // to get the end of week for a particular date, add (7 - weekday) days
  [componentsToAdd setDay:(7 - [weekdayComponents weekday])];
  NSDate *endOfWeek = [calendar dateByAddingComponents:componentsToAdd toDate:self options:0];
  [componentsToAdd release];

  return endOfWeek;
  }

• (NSString *)dateFormatString {
  return @”yyyy-MM-dd”;
  }

• (NSString *)timeFormatString {
  return @”HH:mm:ss”;
  }

• (NSString *)timestampFormatString {
  return @”yyyy-MM-dd HH:mm:ss”;
  }

// preserving for compatibility
+ (NSString *)dbFormatString {
return [NSDate timestampFormatString];
}
@end