object c小代码——日期篇

1、判断两个日期是否是同一天，不要求小时，分钟要一样

   用法

NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];

BOOL datesAreEqual = [calendar isDate:firstDate equalToDate:secondDate toUnitGranularity:NSDayCalendarUnit];

NSCalendar+equalWithGranularity.h

#import <Foundation/Foundation.h>

@interface NSCalendar (equalWithGranularity)

- (BOOL)isDate:(NSDate *)date1 equalToDate:(NSDate *)date2 withGranularity:(NSCalendarUnit)granularity;

@end

NSCalendar+equalWithGranularity.m

#import "NSCalendar+equalWithGranularity.h"

@implementation NSCalendar (equalWithGranularity)

- (BOOL)isDate:(NSDate *)date1 equalToDate:(NSDate *)date2 withGranularity:(NSCalendarUnit)granularity {

    if ([date1 isEqualToDate:date2]) {
        return YES;
    }
    int componentFlags = [self componentFlagsWithGranularity:granularity];
    date1 = [self dateFromDate:date1 withComponentFlags:componentFlags];
    date2 = [self dateFromDate:date2 withComponentFlags:componentFlags];
    return [date1 isEqualToDate:date2];

}
- (int)componentFlagsWithGranularity:(NSCalendarUnit)granularity
{
    int componentFlags = 0;
    for (int i = 1<<1 ; i <= granularity ; i = i<<1) {

        componentFlags = componentFlags | i;
    }
    return componentFlags;

}
- (NSDate *)dateFromDate:(NSDate *)date withComponentFlags:(int)componentFlags {

    NSDateComponents *components = [self components:componentFlags fromDate:date];
    return [self dateFromComponents:components];
}
@end

2、时间若干操作

1 // 当前时间创建NSDate

NSDate *myDate = [NSDate date];

NSLog(@"myDate = %@",myDate);

2 //从现在开始的24小时

NSTimeInterval secondsPerDay = 24*60*60;

NSDate *tomorrow = [NSDate dateWithTimeIntervalSinceNow:secondsPerDay];

NSLog(@"myDate = %@",tomorrow);

3//根据已有日期创建日期

NSTimeInterval secondsPerDay1 = 24*60*60;

NSDate *now = [NSDate date];

NSDate *yesterDay = [now addTimeInterval:-secondsPerDay1];

NSLog(@"yesterDay = %@",yesterDay);

4//比较日期

BOOL sameDate = [now isEqualToDate:yesterDay];

NSLog(@"sameDate = %lu",sameDate);

4.1//获取较早的日期

NSDate *earlierDate = [yesterDay earlierDate:now];

NSLog(@"earlierDate = %@",earlierDate);

4.2//较晚的日期

NSDate *laterDate = [yesterDay laterDate:now];

NSLog(@"laterDate = %@",laterDate);

//两个日期之间相隔多少秒

NSTimeInterval secondsBetweenDates= [yesterDay timeIntervalSinceDate:now];

NSLog(@"secondsBetweenDates= %lf",secondsBetweenDates);

//通过NSCALENDAR类来创建日期

NSDateComponents *comp = [[NSDateComponentsalloc]init];

[comp setMonth:06];

[comp setDay:01];

[comp setYear:2001];

NSCalendar *myCal = [[NSCalendaralloc]initWithCalendarIdentifier:NSGregorianCalendar];

NSDate *myDate1 = [myCal dateFromComponents:comp];

NSLog(@"myDate1 = %@",myDate1);

//从已有日期获取日期

unsigned units = NSMonthCalendarUnit|NSDayCalendarUnit|NSYearCalendarUnit;

NSDateComponents *comp1 = [myCal components:units fromDate:now];

NSInteger month = [comp1 month];

NSInteger year = [comp1 year];

NSInteger day = [comp1 day];

//NSDateFormatter实现日期的输出

NSDateFormatter *formatter = [[NSDateFormatteralloc]init];

[formatter setDateStyle:NSDateFormatterFullStyle];//直接输出的话是机器码

//或者是手动设置样式[formatter setDateFormat:@"yyyy-mm-dd"];

NSString *string = [formatter stringFromDate:now];

NSLog(@"string = %@",string);

NSLog(@"formater = %@",formatter);

转自 http://www.cnblogs.com/xdream86/archive/2012/12/17/2821305.html，感谢原作者的整理收集