NSDate分类,把系统返回的时间与现在进行比较---秀清

//
//  NSDate+Joe.h
//  WeiBo
//
//  Created by 张秀清 on 15/9/17.
//  Copyright (c) 2015年 张秀清. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface NSDate (Joe)

/**
 *  是否是今天
 */
-(BOOL)isToday;
/**
 *  是否是这个月
 */
-(BOOL)isThisYear;
/**
 *  是否是今年
 */
-(BOOL)isThisMonth;
/**
 *  是否为昨天
 */
- (BOOL)isYesterday;

/**
 *  返回'YYYY-MM-DD'的nsdate
 */
- (NSDate *)dateWithYMD;

/**
 *  返回与当前时间的差距
 */
- (NSDateComponents *)deltaWithNow;
@end

//
//  NSDate+Joe.m
//  WeiBo
//
//  Created by 张秀清 on 15/9/17.
//  Copyright (c) 2015年 张秀清. All rights reserved.
//

#import "NSDate+Joe.h"

@implementation NSDate (Joe)

-(BOOL)isToday
{
    NSCalendar *calendar = [NSCalendar currentCalendar];

    int NSCalendarUnit = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay;

    //获取当前的年月日
    NSDateComponents *nowCps = [calendar components:NSCalendarUnit fromDate:[NSDate date]];

    NSDateComponents *selfCps = [calendar components:NSCalendarUnit fromDate:self];

    return (nowCps.year == selfCps.year) && (nowCps.month == selfCps.month) && (nowCps.day == selfCps.day);
}

-(BOOL)isThisMonth
{
    NSCalendar *calendar = [NSCalendar currentCalendar];

    int NSCalendarUnit = NSCalendarUnitYear | NSCalendarUnitMonth;

    //获取当前的年月日
    NSDateComponents *nowCps = [calendar components:NSCalendarUnit fromDate:[NSDate date]];

    NSDateComponents *selfCps = [calendar components:NSCalendarUnit fromDate:self];

    return (nowCps.year == selfCps.year) && (nowCps.month == selfCps.month);

}

-(BOOL)isThisYear
{
    NSCalendar *calendar = [NSCalendar currentCalendar];

    int NSCalendarUnit = NSCalendarUnitYear;

    //获取当前的年月日
    NSDateComponents *nowCps = [calendar components:NSCalendarUnit fromDate:[NSDate date]];

    NSDateComponents *selfCps = [calendar components:NSCalendarUnit fromDate:self];

    return nowCps.year == selfCps.year;
}

/**
 *  是否为昨天
 */
- (BOOL)isYesterday
{
    // 2014-05-01
    NSDate *nowDate = [[NSDate date] dateWithYMD];

    // 2014-04-30
    NSDate *selfDate = [self dateWithYMD];

    // 获得nowDate和selfDate的差距
    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSDateComponents *cmps = [calendar components:NSCalendarUnitDay fromDate:selfDate toDate:nowDate options:0];
    return cmps.day == 1;
}

/**
 *  返回'YYYY-MM-DD'的nsdate
 */
- (NSDate *)dateWithYMD
{
    NSDateFormatter *fmt = [[NSDateFormatter alloc] init];
    fmt.dateFormat = @"yyyy-MM-dd";
    NSString *selfStr = [fmt stringFromDate:self];
    return [fmt dateFromString:selfStr];
}

/**
 *  返回与当前时间的差距
 */
- (NSDateComponents *)deltaWithNow
{
    NSCalendar *calendar = [NSCalendar currentCalendar];
    int unit = NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond;
    return [calendar components:unit fromDate:self toDate:[NSDate date] options:0];
}
@end