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How to get the day component out of an NSDate?

问答 作者：

I have an NSDate object and need an integer of the day. i.e. if we have 25th May 2010, the int should be 25. Is there a simple way to do 开发者_StackOverflow中文版it?

Please consider this post on how to get calendar components from an NSDate. Essentially it will look something like:

NSCalendar*       calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents* components = [calendar components:NSDayCalendarUnit
                                           fromDate:myDate];
NSInteger         day = [components day];

(Don't forget memory management for the above.)

If you only need the "25" part of an NSDate you can get it from a dateFormatter.

Something like:

NSDate *today = [NSDate date];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"dd"];
NSString *dayInMonthStr = [dateFormatter stringFromDate:today];
int dayInMonth = [dayInMonthStr intValue];
[dateFormatter release];
NSLog(@"Today is the %i. day of the month", dayInMonth);

Note that an NSDate is just a timestamp and only has a "day" when considered with respect to a given calendar and time zone. If you want the Gregorian calendar in the current time zone,

NSTimeZone * tz = [NSTimeZone localTimeZone];
CFAbsoluteTime at = CFDateGetAbsoluteTime((CFDateRef)date);
int day = CFAbsoluteTimeGetGregorianDate(at, (CFTimeZoneRef)tz).day;

If you want the UTC day, set tz = nil.

Also, CFAbsoluteTime and NSDate are (as far as I know) based on POSIX time which specifies a 86400-second day, and thus do not handle leap seconds.

Use "EEEE" as the format for full name of the day.

Use "EEE" as the format for the short name of the day.

Example :

- (NSString *)getDayOfTheWeek:(NSDate *)date{
     NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init] ;
     [dateFormatter setDateFormat:@"EEEE"];
     NSString *formattedDateString = [dateFormatter stringFromDate:date];
     return formattedDateString;
  }

I had this problem a while back, and I created the following methods to make everything easier.

Definitions

#define DATE_TYPE_hhmmss [NSArray arrayWithObjects:@"h", @"m", @"s", nil]
#define DATE_TYPE_MMDDYYYY [NSArray arrayWithObjects:@"M", @"D", @"Y", nil]
#define DATE_TYPE_MMDDYYYYhhmmss [NSArray arrayWithObjects:@"M", @"D", @"Y", @"h", @"m", @"s", nil]
#define DATE_TYPE_MMDDYYYYWWhhmmss [NSArray arrayWithObjects:@"M", @"D", @"Y", @"W", @"h", @"m", @"s", nil]
#define DATE_TYPE_MMDDYYYYhhmmssWW [NSArray arrayWithObjects:@"M", @"D", @"Y", @"h", @"m", @"s", @"W", nil]
#define DATE_TYPE_YYYYMMDD [NSArray arrayWithObjects:@"Y", @"M", @"D", nil]
#define DATE_TYPE_YYYYMMDDhhmmss [NSArray arrayWithObjects:@"Y", @"M", @"D", @"h", @"m", @"s", nil]
#define DATE_TYPE_YYYYMMDDWWhhmmss [NSArray arrayWithObjects:@"Y", @"M", @"D", @"W", @"h", @"m", @"s", nil]
#define DATE_TYPE_YYYYMMDDhhmmssWW [NSArray arrayWithObjects:@"Y", @"M", @"D", @"h", @"m", @"s", @"W", nil]
#define DATE_TYPE_FRIENDLY [NSArray arrayWithObjects:@"xx", nil]

Date Methods

Create Date From Values

-(NSDate *) getDateWithMonth:(int)month day:(int)day year:(int)year {
    NSCalendar * calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSDateFormatter * dateFormatter = [[NSDateFormatter alloc] init];
    NSDateComponents * dateComponents = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit) fromDate:[NSDate date]];

    [dateFormatter setDateFormat:@"MM"];
    [dateComponents setMonth:month];
    [dateFormatter setDateFormat:@"DD"];
    [dateComponents setDay:day];
    [dateFormatter setDateFormat:@"YYYY"];
    [dateComponents setYear:year];

    NSDate * result = [calendar dateFromComponents:dateComponents];

    return result;
}

-(NSDate *) getDateWithMonth:(int)month day:(int)day year:(int)year hour:(int)hour minute:(int)minute {
    NSCalendar * calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSDateFormatter * dateFormatter = [[NSDateFormatter alloc] init];
    NSDateComponents * dateComponents = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit) fromDate:[NSDate date]];

    [dateFormatter setDateFormat:@"MM"];
    [dateComponents setMonth:month];
    [dateFormatter setDateFormat:@"DD"];
    [dateComponents setDay:day];
    [dateFormatter setDateFormat:@"YYYY"];
    [dateComponents setYear:year];
    [dateFormatter setDateFormat:@"HH"];
    [dateComponents setHour:hour];
    [dateFormatter setDateFormat:@"MM"];
    [dateComponents setMinute:minute];

    NSDate * result = [calendar dateFromComponents:dateComponents];

    return result;
}

-(NSDate *) getDateWithMonth:(int)month day:(int)day year:(int)year hour:(int)hour minute:(int)minute second:(int)second {
    NSCalendar * calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSDateFormatter * dateFormatter = [[NSDateFormatter alloc] init];
    NSDateComponents * dateComponents = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit) fromDate:[NSDate date]];

    [dateFormatter setDateFormat:@"MM"];
    [dateComponents setMonth:month];
    [dateFormatter setDateFormat:@"DD"];
    [dateComponents setDay:day];
    [dateFormatter setDateFormat:@"YYYY"];
    [dateComponents setYear:year];
    [dateFormatter setDateFormat:@"HH"];
    [dateComponents setHour:hour];
    [dateFormatter setDateFormat:@"MM"];
    [dateComponents setMinute:minute];
    [dateFormatter setDateFormat:@"SS"];
    [dateComponents setSecond:second];

    NSDate * result = [calendar dateFromComponents:dateComponents];

    return result;
}

Get String From Date

-(NSString *) getStringFromDate:(NSDate *)date dateType:(NSArray *)dateType {
    NSString * result = @"";

    NSCalendar * calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSString * format = @"";

    NSDateComponents * dateComponents = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit | NSWeekdayCalendarUnit) fromDate:date];

    NSInteger year = [dateComponents year];
    NSInteger month = [dateComponents month];
    NSInteger day = [dateComponents day];
    NSInteger weekday = [dateComponents weekday];
    NSInteger hour = [dateComponents hour];
    NSInteger minute = [dateComponents minute];
    NSInteger second = [dateComponents second];

    if (dateType != nil) {
        for (int x = 0; x < [dateType count]; x++) {
            if (x == ([dateType count]-1)) {
                if ([[dateType objectAtIndex:x] isEqualToString:@"Y"]) {
                    format = [format stringByAppendingFormat:@"%d", year];
                } else if ([[dateType objectAtIndex:x] isEqualToString:@"M"]) {
                    format = [format stringByAppendingFormat:@"%d", month];
                } else if ([[dateType objectAtIndex:x] isEqualToString:@"D"]) {
                    format = [format stringByAppendingFormat:@"%d", day];
                } else if ([[dateType objectAtIndex:x] isEqualToString:@"W"]) {
                    format = [format stringByAppendingFormat:@"%d", weekday];
                } else if ([[dateType objectAtIndex:x] isEqualToString:@"h"]) {
                    format = [format stringByAppendingFormat:@"%d", hour];
                } else if ([[dateType objectAtIndex:x] isEqualToString:@"m"]) {
                    format = [format stringByAppendingFormat:@"%d", minute];
                } else if ([[dateType objectAtIndex:x] isEqualToString:@"s"]) {
                    format = [format stringByAppendingFormat:@"%d", second];
                }
            } else {
                if ([[dateType objectAtIndex:x] isEqualToString:@"Y"]) {
                    format = [format stringByAppendingFormat:@"%d|", year];
                } else if ([[dateType objectAtIndex:x] isEqualToString:@"M"]) {
                    format = [format stringByAppendingFormat:@"%d|", month];
                } else if ([[dateType objectAtIndex:x] isEqualToString:@"D"]) {
                    format = [format stringByAppendingFormat:@"%d|", day];
                } else if ([[dateType objectAtIndex:x] isEqualToString:@"W"]) {
                    format = [format stringByAppendingFormat:@"%d|", weekday];
                } else if ([[dateType objectAtIndex:x] isEqualToString:@"h"]) {
                    format = [format stringByAppendingFormat:@"%d|", hour];
                } else if ([[dateType objectAtIndex:x] isEqualToString:@"m"]) {
                    format = [format stringByAppendingFormat:@"%d|", minute];
                } else if ([[dateType objectAtIndex:x] isEqualToString:@"s"]) {
                    format = [format stringByAppendingFormat:@"%d|", second];
                }
            }

            if ([[dateType objectAtIndex:x] isEqualToString:@"xx"]) {
                format = [NSString stringWithFormat:@"Year: %d, Month: %d, Day: %d, Weekday: %d, Hour: %d, Minute: %d, Second: %d", year, month, day, weekday, hour, minute, second];
            }
        }
    } else {
        format = [format stringByAppendingFormat:@"%d|", year];
        format = [format stringByAppendingFormat:@"%d|", month];
        format = [format stringByAppendingFormat:@"%d|", day];
        format = [format stringByAppendingFormat:@"%d|", weekday];
        format = [format stringByAppendingFormat:@"%d|", hour];
        format = [format stringByAppendingFormat:@"%d|", minute];
        format = [format stringByAppendingFormat:@"%d|", second];

        format = [NSString stringWithFormat:@"%d|%d|%d|%d|%d|%d|%d", year, month, day, weekday, hour, minute, second];
    }

    result = format;

    return result;
}

Example

NSDate * date = [self getDateWithMonth:12 day:24 year:1994];
NSString * dateInString = [self getStringFromDate:date dateType:DATE_TYPE_MMDDYYYY];

int month = [[[dateInString componentsSeparatedByString:@"|"] objectAtIndex:0] intValue];
int day = [[[dateInString componentsSeparatedByString:@"|"] objectAtIndex:1] intValue];
int year = [[[dateInString componentsSeparatedByString:@"|"] objectAtIndex:2] intValue];

NSLog(@"String of Date: \"%@\"", dateInString);
NSLog(@"Month: %d", month);
NSLog(@"Day: %d", day);
NSLog(@"Year: %d", year);

The method [self getDateWithMonth:12 day:24 year:1994] returns an NSDate object which is usually hard to read, so you can use [self getStringFromDate:date dateType:DATE_TYPE_MMDDYYYY] to get a string of an NSDate object.

Use the definitions (macros) to specify the format of the date you would like to get in the string.

For example: DATE_TYPE_hhmmss would return the Hour|Minute|Second, DATE_TYPE_MMDDYYYY would return the Month|Day|Year, DATE_TYPE_MMDDYYYYhhmmss would return the Month|Day|Year|Hour|Minute|Second, DATE_TYPE_MMDDYYYYWWhhmmss would return the Month|Day|Year|Weekday (#)|Hour|Minute|Second

and so on...

Console Log

2012-04-29 13:42:15.791 Atomic Class[1373:f803] String of Date: "12|24|1994"
2012-04-29 13:42:15.793 Atomic Class[1373:f803] Month: 12
2012-04-29 13:42:15.794 Atomic Class[1373:f803] Day: 24
2012-04-29 13:42:15.794 Atomic Class[1373:f803] Year: 1994

继续阅读：nsdate

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