iOS - NSDate分类-判断时间是否为今天,昨天,一周内,年月日

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#import <Foundation/Foundation.h>

@class  JYChatMessageModel;

@interface NSDate (extension)

//判断时间戳是否为当天,昨天,一周内,年月日
+ (NSString *)timeStringWithTimeInterval:(NSString *)timeInterval;

@end

#import "NSDate+extension.h"

@implementation NSDate (extension)


+ (NSString *)timeStringWithTimeInterval:(NSString *)timeInterval
{

    NSDate *date = [NSDate dateWithTimeIntervalSince1970:timeInterval.longLongValue/1000]; //此处根据项目需求,选择是否除以1000 , 如果时间戳精确到秒则去掉1000

    NSDateFormatter *formatter = [[NSDateFormatter alloc]init];

    //今天
    if ([date isToday]) {

        formatter.dateFormat = @"HH:mm";

        return [formatter stringFromDate:date];
    }else{

        //昨天
        if ([date isYesterday]) {

            formatter.dateFormat = @"昨天HH:mm";
            return [formatter stringFromDate:date];

            //一周内 [date weekdayStringFromDate]
        }else if ([date isSameWeek]){

            formatter.dateFormat = [NSString stringWithFormat:@"%@%@",[date weekdayStringFromDate],@"HH:mm"];
            return [formatter stringFromDate:date];

            //直接显示年月日
        }else{

            formatter.dateFormat = @"yy-MM-dd  HH:mm";
            return [formatter stringFromDate:date];
        }
    }
    return nil;
}


//是否在同一周
- (BOOL)isSameWeek
{

    NSCalendar *calendar = [NSCalendar currentCalendar];
    int unit = NSCalendarUnitWeekday | NSCalendarUnitMonth | NSCalendarUnitYear ;

    //1.获得当前时间的 年月日
    NSDateComponents *nowCmps = [calendar components:unit fromDate:[NSDate date]];

    //2.获得self
    NSDateComponents *selfCmps = [calendar components:unit fromDate:self];

    return (selfCmps.year == nowCmps.year) && (selfCmps.month == nowCmps.month) && (selfCmps.day == nowCmps.day);
}


//根据日期求星期几
- (NSString *)weekdayStringFromDate{

    NSArray *weekdays = [NSArray arrayWithObjects: [NSNull null], @"星期天", @"星期一", @"星期二", @"星期三", @"星期四", @"星期五", @"星期六", nil];

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

    NSTimeZone *timeZone = [[NSTimeZone alloc] initWithName:@"Asia/Shanghai"];

    [calendar setTimeZone: timeZone];

    NSCalendarUnit calendarUnit = NSCalendarUnitWeekday;

    NSDateComponents *theComponents = [calendar components:calendarUnit fromDate:self];

    return [weekdays objectAtIndex:theComponents.weekday];

}




//是否为今天
- (BOOL)isToday
{
    //now: 2015-09-05 11:23:00
    //self 调用这个方法的对象本身

    NSCalendar *calendar = [NSCalendar currentCalendar];
    int unit = NSCalendarUnitDay | NSCalendarUnitMonth | NSCalendarUnitYear ;

    //1.获得当前时间的 年月日
    NSDateComponents *nowCmps = [calendar components:unit fromDate:[NSDate date]];

    //2.获得self
    NSDateComponents *selfCmps = [calendar components:unit fromDate:self];

    return (selfCmps.year == nowCmps.year) && (selfCmps.month == nowCmps.month) && (selfCmps.day == nowCmps.day);
}



//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;
}

//格式化
- (NSDate *)dateWithYMD
{
    NSDateFormatter *fmt = [[NSDateFormatter alloc] init];
    fmt.dateFormat = @"yyyy-MM-dd";
    NSString *selfStr = [fmt stringFromDate:self];
    return [fmt dateFromString:selfStr];
}