自己新添加的一些NSDate的分类方法

////*****.m文件

#import "NSDate-Helper.h"

@implementation NSDate(Helpers)

 

/*

 * This guy can be a little unreliable and produce unexpected results,

 * you're better off using daysAgoAgainstMidnight

 */

 //获取年月日如:19871127.

- (NSString *)getFormatYearMonthDay

{

 NSString *string = [NSString stringWithFormat:@"%d%02d%02d",[self getYear],[self getMonth],[self getDay]];

 return string;

}

 //返回当前月一共有几周(可能为4,5,6)

- (int )getWeekNumOfMonth

{

 return [[self endOfMonth] getWeekOfYear] - [[self beginningOfMonth] getWeekOfYear] + 1;

}

//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