IOS类扩展之日期操作NSDate+Helpers

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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

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